I hate myself, I feel like such a failure.
Oh no, why do you feel that way?
Because my grades are so bad and I may not get into a good college.
Rather than dwelling on your failures, why don't you think about how you can improve yourself? You'll probably never be happy if you don't start taking a positive attitude towards yourself.
I'll feel good when I find someone who will love me.
It sounds like you are under a lot of pressure and a lot of that pressure is coming from yourself. Rather than only being happy if you get good grades or find love, focus on your attributes and what is good about being you. It's understandable to feel down but don't let it take over.