However, I don't know why, lately I'm having strange imaginations of women, which, as a matter of fact, disgust me. For instance, when I'm thinking about men while masturbating, girls show unexpectedly and my libido falls. What is more, I think that I subconsciously want to reassure myself of being gay. Women do not attract me sexually at all (although I like them and have quite nice girl colleagues, this is only conversation and school matters). Strange as it may sound, it's really a big problem to me, and I fear falling into depression. Is there a way of getting rid of those particular imaginations - which are unwelcome by me? Please help...
I normally take a psychological approach to answering questions like this but this time I'm going to draw from a course I took on the practice of meditation.
In this course I learned that thoughts are not the self or the mind. Thoughts can come from the mind, but there is a mind distinct from our thoughts that is a witness to goings on of the world. This witness can see thoughts and react to them but it can also be disciplined to just let thoughts pass without labeling or placing judgement.
My advice to you is to just let these thoughts pass without labeling or placing judgement. If you are gay, let your body behave gay. If your sexuality is more flexible, let your body behave in a sexually flexible manner.
The most important thing is to be accepting of yourself and healthy. You do not need to reinforce to yourself that you are gay by trying to actively dislike women sexually, particularly since disliking women sexually does not equal being gay. Just go with what is healthy and feels good.
What's the worst that could happen in your current mode of thinking? You could try out a vagina, and chances are it probably won't hurt you . . . and if you don't like it you could just go back to cock.
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I don't think your distress is all that unusual for somebody young and trying to figure out their sexuality. I have not heard of an out gay person trying to deny heterosexual thoughts, but I have certainly heard of a closeted gay person trying to deny there homosexual thoughts. I imagine in both case the answer is the same, give yourself a break, relax, try out what you are attracted too with the only rule being be healthy and safe.