Please listen to your girlfriend. She cares about you. She cares enough to give you really good advice. You need a therapist to help you come to terms with your past and to take charge of your present and future.
Many communities have programs for teens who need treatment but can’t afford it. Please talk to your school guidance counselor about resources that are available. If free therapy isn’t offered locally, consider joining a support group either here at PsychCentral or in your town. Sometimes churches offer guidance through youth groups and individual conversations. There are also excellent books that can help you sort out your feelings. Explore your local bookstore. This article might give you some ideas as well: https://psychcentral.com/lib/when-you-cant-afford-psychotherapy/
Your situation is not unique. Many, many people do not get the family they wish they had. But family is not just about blood relationships. We can each create real “family” with good friends we take into our hearts. Those connections are just as real, just as precious and just as loyal as those that some people are fortunate enough to be born to. I hope you will start embracing other people to make yourself a strong and loving support system that will last a lifetime.
I wish you well.