How do I (20m) mend this wound she (21F) gave me?

For context me and my gf were moving out of a master bedroom we had been renting for a year and some change. The landlords decided they didn’t want us renewing our lease. I work 3rd shift and she had today off so she said she’ll spend all night packing with her friend as we had to move out in a couple days.

For context on our relationship we were high school sweet hearts and someone even after 5 years of dating i was still crazy about. She was the most interesting person in the room and i would’ve jumped in front of a bus for her. We had plans to get married in a 5 months in a $4,000 wedding my mom was helping us with. She didn’t have the best upbringing as a child and has some terrible events happen in her life. I doubled down every time and wanted to be there for her. It always amazed me how resilient she was even if it was a fake face she was putting on. I was proud to be with her. Through thick and thin she was always someone i could trust and the same for her with me. When her family didn’t treat her so well (in which was often the case) i dreamed of nothing but starting a life together and saving her from that tragedy.

After the High school she went to the navy and i went to college. I waited for her. we had agreed to try to make it work and i gave it my all. in fact I couldn’t do anything. I became borderline depressed and never left my dorm. never interacting with someone. i waited every Friday for her phone calls and checked the mail everyday for her letters. Eventually all the school work caught up to me and i dropped out. (after almost a year) She also couldn’t pass basic training tests due to health complications. i was so happy when she came back. my mom took us to the florida keys and Disney. Disney was fun but a bit too hot but fishing off the dock with her in the keys is memory i’ll cherish forever.

after this i asked her to marry me and she agreed. we moved out soon after this and started our own lives together. we had three dogs and a fairly nice house to stay in. our roomates and landlords were terrible. We continued on and i counted down everyday til our wedding. i was so excited to give this girl my whole future. As of a couple months ago she started voicing her concerns with bills and her mental health. I didnt always know what to do but i tried to help her. Eventually got to the point where she started breaking down. we both agreed it would be best if she went to a mental hospital and got help. i took her and they admitted her for a week. this past week. i called her every day and checked up on her. i also had to pack our stuff up, take care of the dogs, and work. i was getting a max of 4 hours of sleep each day. i told her i was fine and she should focus on herself and that i was so proud of her for doing something so scary.

When she got out i was there and was so happy. she said she finally felt normal. i took her to go eat and show her the new house. She told me her and her friends would finish packing. one friend got sick and didn’t come. the other friend is a guy but i trusted her and plus nothing comes of jealous feelings. after work i came home to help and opened what was our bedroom door and it was obvious they had sex. i closed the door and just gasped. the rush through my body fierce and it felt like i had been shot. i walked in and started packing up the rest of my stuff. walked back up and said “hi (guys name)” and punched him in the face. i asked if he was ok and if he was going to punch me back. he said he was ok and understand how I felt. i told her goodbye and gave her the ring she gave me and i had worn for 3 years.