'Do not worry about your difficulties in mathematics. I can assure you mine are still greater' - Albert Einstein
First of all, stop for a minute, take a breath and relax a little.
Now think about what it is you want to do in the future. Not what your parents want you to do, or what you think you should do - what you want to do. Then think about what grades and A levels you need to achieve that. You may want to go into something that has nothing to do with mathematics or that you don't want to go to uni at all. Either way, you need to do what you want to do or you'll be miserable.
Then you should speak to your teachers. Ask them if they think Maths at A level is a good idea for you, and if you're that certain you want to do it, what you should do to get to a stage where it would be a good idea. Most schools should accept a 7 for A level, but if that is you're final grade, not only is that roughly equivalent to an A (a 9 is better than an A*), Further Maths is probably not the best idea.
Also, universities don't really care where you got your A levels - they are more concerned with what results you get. But all the A*s in the world are no good if you do nothing outside of the classroom. If you know that studying Maths or Further Maths at A level means you will constantly be studying, then don't take it and do some volunteering instead - even Oxford turn down four A* grades if you do nothing outside of studying.
Whatever you decide, if you apply yourself, you'll get the best grade you can, and that is all that should matter.
Your teachers will be the best to go to for advice though. I'd also advise you speak to your pastoral team and tell them that your parents are pressuring you, for lack of a better term. Someone at school will be able to help you.
Good luck, and I hope it all work so out for you.