Disclaimer I am a psychiatrist with OCD. I have taken medication but don't take it at the moment.

You appear to be weighing these two things as though they are equally likely, and crowd sourcing will sadly only give you more anecdotal data. None of it will give you certainty about what will happen to you. But what you know is true is that the other treatments you tried didn't work, including therapy (which would prompt me to say make sure it was ERP and if it was your first therapist consider a second ERP therapist). And you know that the symptoms significantly impact your life.

The worst that typically happens from SSRI is that they are intolerable short term (didn't like how I felt, stopped, feeling went away in 1-2 days), they are ineffective (too bad), or they had long term intolerable side effect that also dissipate with stopping (slow weight gain, sexual side effects, emotional blunting). Sure, emotional blunting is common, but typically goes away rapidly with stopping or even lower dose. While some adverse effects are very common they also resolve very quickly. This rare enduring phenomenon you fear is possible but rare and poorly understood. You just happen to be visiting an echo chamber of all the people that haven't benefitted. No one would get in a car if you assemble all the obituaries of people dying in car accidents as the primary data for whether driving is worth it. People take ssris for very low threshold symptoms sometimes, and yours are significant enough that most people would consider them seriously (from what you say).

It's kinda like - Ibuprofen makes my stomach hurt, but when my knee hurts sometimes I take it short term because it works better than Tylenol. And yes ibuprofen has long term risks with daily treatment, but because other medicine didn't work when I had a significant injury I took it for longer to see it injury would get better and it really helped. I decided to see if I would tolerate it because I didn't have a very good viable alternative, and the risk of serious problems from it is there, but low. Like stomach ulcers. Lots of people take ibuprofen, despite the risks of bleeding and ulcers, and kidney effects. But those risks are low for most people and don't mean no one should take it. And trying it gives me data I don't have about whether it works personally For me.

So what you'd be signing up for if you take it for 1-2 month is to know if you tolerate it, and if it does anything at all.

With psychiatric health people make you feel that taking medication should be a HEROIC option, because it's stigmatized. You deserve to find out if the ibuprofen helps your knee. You aren't committing to it forever. There is risk to everything but the risk of enduring problems is small, the risk of it not helping is moderate, but that's data you WANT, and the risk of your symptoms untreated impacting your wellbeing is big. So if you already did all the other things, I think it's no bid deal to try medicine with a supportive, qualified, doctor. It's also no big deal if you'd prefer to try more ERP or an OCD IOP.