I agree with >>3 on this. If you live with your family tell them and have them help you. Quitting on your own is going to be extremely difficult, especially if you have outside influences going against you.
Although you may have had great times with your friends, if being clean is something really important to you, you really should try and break ties with anything associated with your past life. For some people it's easy to stay clean while being with people on drugs, but from what you've said it sounds like you're not one of those people. It all boils down to what's most important-- becoming clean and not messing up your future, or staying with your current friends who influence you in a way you don't really want to be influenced in.
You can always find more friends and have better times than before (and be able to remember them...), but if you mess up too much at this time, it's really hard to straighten yourself out later.
Good luck!!