hmm.
maybe you should talk to your mum about how much you hate being compared to others'? parents always compare their kids to everyone elses, its natural. i hate it too, its done so much, but i always tell them that i am me and that no-one else will be like me/i will never be like anyone else, no matter how much they try/want it to happen. i've learnt to ignore things people say to me that i really despise, and it makes me seem so ignorant but i really don't care now.
its always helpful if you talk to someone, the internet can do so much but talking to someone personally helps, even if they don't take it well, at least you can't say you didn't try.
try not to take it too seriously. exams cause stress for everyone, but they happen once so make the most of them.
as for people bombarding you with their problems, it sounds selfish but only help those you know will help you back. i've made the mistake of helping 'friends' who won't speak to me again, but then again i've done them a favour so whether they appreciate it or not, its not my fault i'm nice!