Dear student
This kind of relative-cousin pressure is common.Since you are more conscious on your self-study then, I would say that you are going on right track.You need guidance from yyour teachers and since you said that you have joined coaching in yor city then, I am expecting that the coaching and the faculties would be good over there, if not kindly change it as there is no point of wasting time and money on it otherwise.
Carry on with you self study, be confident enough and never leave hard work.Ask doubts from teachers though the ones of your school or your coaching.In fact involve your cousin, ask him “do you know how to solve this” in a challenging mode so that he will involve in your doubt-solving activity.