You feel like you are an abnormal age to be coming out and it makes you feel worse about coming out. The truth is that the age does not matter at all. Because you may (or may not, I don't know!) be older than the average person in this generation who comes out, you are letting that fuel your worry. All that worry is not really because of your age, it is just because of the scary concept of coming out. You just tell yourself it is worse because you are older.
I think people will support you. Maybe some of them suspect it anyway and are just waiting for you to be ready to tell people. If your parents are very very anti-gay then you have a problem. Otherwise though, I think it is fine. If someone were to be angry at your sexuality, it is because they are denying it, they don't want you to be like that. But in the end, them shouting about it isn't going to change the fact of your sexuality. Denial isn't really an option. This is why most mature adults will just accept it with no fuss. Some people might not approve or it might make them feel a bit awkward, but as long as you keep being you then they can still like you for you. What I'm saying is, don't suddenly start gossiping non stop about what sex you had recently or how incredibly fit that person who walked past is. Unless you did that normally anyway, then people will simply start disliking you for that, nothing to do with your sexuality. That is a problem I have with a friend who came out recently. He suddenly seems obsessed with his own ego and making good impressions on strangers with his newfound confidence and charisma, and doesn't appreciate the people who are there to support him. All the while saying that no one appreciates him.
As long as you don't start acting stupid, you have no problems. It's difficult that this all happened near exams, but there is always something important going on. I read a thread a while ago about a couple who didn't know whether to start a relationship or not because of impending AS level exams. To be honest though it's either going to be AS levels, A levels, new college, different colleges/unis, uni exams, moving house, new job, difficult busy time for job, family crisis... the list is endless, there is always something that makes the situation less than ideal.