How do I explain to my parents how I feel.....?

That sounds like a pretty tough situation to be in.. I would suggest maybe joining a club or some type of activity group for your school or spending your time doing a hobby. Joining a gym or doing yoga or learning a new skill can take your mind off of what is bothering you. It's hard but your almost there, and you don't want to give up. Just push through it, and you will be very happy when you complete your schooling!