Hi,
I'll mention as a start that I'm not a doctor or therapist, so only talking from my own experience. You seem to be under considerable distress, have you considered seeing a doctor about this? Regardless of your country and whether you are or not overage, you should be able to access confidential, professional treatment.
At this stage I cannot say if it is or isn't OCD, only a proper medical diagnosis can ascertain this. Regardless, whatever condition it may be is clearly causing a lot of distress. Before I go ahead and say anything else, I would just like to mention that there are
thousands of documented OCD cases in the world (any many more undocumented!). You are not alone in your struggle, and many people (including myself!) now find that they have made improvements that they genuinely wouldn't have thought possible. Stay strong, you are doing a great job at coping with your difficulties and will make even further progress!
if I find my own male body arousing then that must mean I'm attracted to male bodies.
Does it? There are a variety of reasons why your own nudity might cause arousal, and you shouldn't jump to the conclusion that you are attracted by males. For example, nudity is often associated to sexuality and sexual relations. Your body and mind might be responding to a general situation that resembles, for example, the beginning of a sexual relation with a woman.
Generally speaking, focusing on nudity, nakedness, sexual organs, etc. will provoke an arousal in the body. This has nothing to do with being attracted by males, females, both or neither. It's a purely physical reaction.
I know that being aroused by yourself is different, but this arousal is getting too big.
I'll just put it there, homosexuals are usually attracted by other males, not by their own penis exclusively. This might very well be a by-product of HOCD.
I'll ask you the same question I asked myself when dealing with intrusive thoughts. Do you
identify with the thoughts? Do they feel like they describe you adequately, or are they egodystonic? (Ie: Do not describe you/Are the opposite of what you want to be)
Somebody who is heterosexual feels naturally attracted to women. Thoughts of being with them, entering a relationship, being intimate with a female partner are usually welcome and treasured.
The same goes for homosexuality. Somebody who finds they are homosexual might find it difficult to deal with because they are worried of the reaction of their parents, peers and community. They might also feel disorientated by it, especially if they were brought up in a socially conservative environment. Usually, however, they will not question the genuinity of the feelings of attraction towards other males.
In your case, however, you spoke a lot about being afraid of being homosexual, but not about "feeling" homosexual. OCD is the disease of doubt. You will doubt yourself over and over, but thiss does not mean the threats or worries have any substance.
From the way you described it, it would appear to me you are not attracted by other men, but could potentially need help to develop coping strategies for OCD. Hence, I strongly advise you seek professional support. If you do not know where to start, your GP (family doctor) is usually the best starting point.
I hope this helps!