I dont know what to do. I have been with my GF for 2 and a half years and i just found out a week ago she was cheating on me for two or three months. She says she still wants to be with me and I want to be with her but I dont know how to trust her.

She lied to me about so much. But she has also helped me with so much. I need her like I need no other. But my heart is dust. I dont know what to do. I dont know how to trust her. I dont even think Im worth the effort. I hate myself to the point where I dont want to look at myself in the mirror. I feel like everything is my fault. I need advice. Anyone willing to help?