It sounds like you haven't met the right friends yet. Honestly a lot of personal problems can be because you are not surrounding yourself with the right people. Is there really nobody in your life who would support your coming out? If not, you must start looking for new friends. I advise against assuming that other gay people will always be the friends you need. You need friends who you connect with on grounds other than sexuality who support you living your life honestly and openly as a gay man. Shared sexual orientation often does not provide solid and durable ground for friendship.

I am lucky I never felt shame about gay sex. I have self-respect, a lot of pride (unfounded, perhaps), and a fair amount of fuck-the-world defiance, and these qualities helped me in the beginning. Therefore it is hard for me to understand why some guys feel shame after sex; and yet, I belive you, and sympathise. I'm not a psychologist, but I assume building up your self-respect---it is a practice---is going to help you move beyond this. You should also probably find a therapist to help you work through these issues. Talk therapy will change your life.

You are only 21, don't miss out on sexual experience while you are young and your body is ripe and beautiful. It is literally the hottest, most glorious time for any gay man, and you should be enjoying it!