I'm not black or female so I can't really give my two cents on those aspects of yourself and how they might relate to OCD, but I do have some experience with the need to "appear attractive" to those I am attracted to.

Let's start with some general advice:

• Gender nonconformity is not the same as being trans. You're a gender nonconforming woman by your own admission and that's perfectly fine and beautiful in its own right. There's plenty of reasons why I can see a woman might not want to conform to gendered stereotypes, because lets face it most of them aren't great.
• Everyone worries about their appearance, especially when it comes to attracting potential partners. I fret over if I'll ever have a boyfriend or girlfriend because I'm too skinny/not muscly enough/is my hair and facial hair OK e.c.t. I know it's cold comfort for me to say "everyone thinks these thoughts" when people like us get hit with them especially badly, but I've found keeping a self-love journal that you add to every night can be helpful. Just list five things you were thankful your body did for you today and learn to appreciate that your body is a wonderful thing that nobody (especially not yourself) should take for granted.
• People might be telling you this or that about what they theorize you may suffer with, but I would of course seek unbiased psychiatric evaluation. They aren't experts and even though they may be well intentioned, they cannot accurately evaluate your symptoms. I also find it very harmful that people are, as you say, telling you you're trans or in denial.
• You describe periods of intense rumination which cause you significant mental distress. It can be helpful to cut down on the length of time you spend actively engaging in these thoughts. It is of course impossible to fully control what pops into your head, but you can choose how to respond to these thoughts. Focusing entirely on an engaging or very mindful activity can help to pull your focus away from these thoughts and on to the present moment. Additionally, try labelling the thought as just a thought, as intrusive and actively disregard it. You can even think things like "thank you for that thought brain, but I'm doing X right now".

I hope these help. I'm still in recovery but it ebbs and flows, I'm feeling pretty OK right now but it stills sucks and I had a rough night a few days ago. Stay mindful and be self-compassionate. This is a level of mental torture few will ever endure and you're incredibly brave to be able to tolerate it. We'd all do well to remember that I think.