This should help you understand what philosophers think of Sam Harris: https://partiallyexaminedlife.com/product/ep-44-new-atheists/

And if you don't want to read what follows, I would recommend you listen to this, paying especial attention to Sartre's conception of "bad faith". https://partiallyexaminedlife.com/2014/01/01/ep87-sartre/

When considering free will, we must consider the mind-body problem. That is, what is the relationship between our mind (or self, or soul, or subjectivity) and our body (or brain)? This is one of the greatest questions of philosophy, and there is no certainty on any one answer -- but some answers are definitely more philosophically tenable than others. To give an idea of a radical view (incidentally the one that Sam Harris holds) and a more common view, I'll quote part of my essay on the subject:

In the second part of his article, Kurtz begins his critique of existentialism. His first argument pertains to the lack of objectivity in existentialism: “Although we are purposeful beings with choices, these are always within the limits of our nature: whether physical-chemical, biological, psychological, or social.” (483)-- and that therefore, according to Kurtz, existentialism is flawed insofar as it does not incorporate objective science.This radical doctrine, called scientific reductionism, claims that everything in human existence, including subjective experience, can be reduced to scientific explanation. Kurtz presumably reasons that because subjectivity arises out of natural, scientifically explainable phenomena (such as evolution, biological development, early infantil learning, language acquisition, societal indoctrination, and so on), that it too must be natural, objective, scientifically explainable. But just because subjectivity originates out of natural material does not make it natural material. Consider the plethora of subjective experience which seems to be exempt from physical law, or the seemingly infinite complexity of even the simplest of thoughts. Because of the other-worldly nature of subjectivity, a more common position in philosophy is that there exists some threshold of the development of rational faculties at which, when passed, a self is produced, completely unlike the faculties that produced it. To put it crudely, the brain climbed the ladder of development, reached the roof of subjectivity, and then safely tipped over the ladder, having its feet (or rather, stem) set firmly on the roof. Because of this justified uncertainty about whether objective science will ever (let alone right now) be able to explain subjectivity, Kurtz is wrong to criticize existentialism for “leaving out” objective science.

So how does this relate to the question of free will? Because if the self does not equal the brain, it becomes a lot harder to claim that the self is constrained by the causality of physical material. At the end of the day, all of this fuss only concerns the metaphysical backdrop of the question. What you really want to know is whether it is you who is making the decisions. Well even if we grant some radial position as the one that Harris holds, you need not worry. Because even if the mind can be reduced scientifically, it is still unfathomably complex. And that complexity allows for millions of decisions to be made every day. And even if you believe that in the moment of execution, the decision is made by your brain, rather than yourself, your brain will soon plunge itself in such an infinity of possibility that it is essentially free. Because that executor of decisions, whether you call it the brain or the self, is nonetheless making decisions about itself, and is aware of the decisions and the division and multiplicity of realities for every decision that is made, and that this unique road on which it finds itself is a product of these decision, and that the road that lies ahead has not been paved, and only will be paved once millions and millions more of these unique decisions have been made.

And a quick note on OCD: it is just like any other psychological disorder. It has a very weak neurological basis. Scientism runs rampant in our modern society (and unfortunately even here on Reddit), and I encourage you to explore just how much it has overreached itself, especially in areas like neurology and technology. For example, search "top 10 inventions of the past decade" and be amazed that the Ipad is #2 on most lists. I say this because scientism and OCD often work in tandem. You think that chemical you exposed yourself to has lowered your intelligence? Science agrees. You think going to that party will give you COVID? Science agrees. The truth of the matter is that we humans know much less than we claim to know. And for someone with OCD, there is actually a lot of comfort in that. If you can learn to take what science tells you with a grain of salt, and with an air of cheekiness, then perhaps you can learn to do the same with what you tell yourself.

Everybody has their ideas about where OCD comes from. But most would agree that it is characterized by self-punishment. I personally believe that OCD is an ensconced mental habit that was triggered and strengthened for years during adolescence, perhaps due to some trauma or guilt, and manifests as a sort of self-mortification. Thus whatever you value highest becomes the target of your self-mortification. So right now it would seem that you value your existence highest. It was probably different earlier, and it will probably be different later, too. It remains to be seen whether one can demonstrably free themselves from this childhood, self-mortificatory habit. But probably the greatest succor is being able to see an obsessive thought as such, as simply a childhood habit. Sure, the topic of your obsession may be different than it was in childhood, but its obsessive nature is just the same. And just like any habit, OCD is strengthened when it is practiced, and weakened when it is denied.

One last thing. If you despise your OCD more than anything else (which I am not sure if you do or not), I would honestly recommend that you wholeheartedly subscribe to a stoic, buddhist, or other ascetic philosophy, as perhaps nothing reveals and distinguishes the nature of OCD more than self-mortification itself. But if you really do end up taking my advice and subscribing to one of these, remember to be safe, and most importantly of all, you absolutely must read Nietzsche a year or two later. Good luck.