How can i get better from this depression i'm in?

First of all, you have a right to be upset. What your g/f did was not funny, and if she thinks that is was, she has a lot of maturing to do. I don't know how old you are, but you are never too young to be respectful of your partner's feelings. She knowingly picked the one issue that she knew would upset you the most. You will not have the anger/depression problem get any better until you have an open and honest talk with your g/f. What she did was cruel, she knows it, and if hurting you like that is funny to her, maybe you have picked the wrong person to be your g/f. She needs to understand how hurtful her behavior was, and you have every right to expect her to realize that this is not what you do to a person you care for.

Obviously people your age are starting to experiment, but that is not the defining reason to have sex. There is no time table for sex, it is something that should be taken seriously and hopefully will have some deep feelings involved with it. When it does happen, please protect yourself and your partner. 1 mistake could lead to a child being born that would impact you your entire lifetime Also remember that you are getting to an age when sex will be a natural part of a committed relationship. Be a decent person and remember it often impacts women differently than men, so don't ever force of guilt someone into doing something they are not ready for.

It's OK to be pissed. Just don't make stupid mistakes because of that anger. You have a lot of life ahead of you. Hang in there. Hope this helps!