My (24F) boyfriend (25M) has been friends with a girl(25F) for longer than our relationship. She was always kind and respectful about our relationship… at least till last month, or maybe I just never got the signs. I had no problem with her as I didn't think it was my place to interfere between them since they had been friends for a longer time. As the title suggests, he told me he had a business trip for a week and had to go. I didn't question it at first. But while he was gone, I noticed that she posted a photo on her ig that was from the same place as his business trip. 2 hours later, the post gets deleted. It was suspicious so I digged a little deeper. I found out from some common friends that she had also left for a "Solo trip" for the same week.
During the trip, he didn't pick up my calls, answer or read my texts, didn't contact me whatsoever. I didn't know what to feel about this. If he just wanted to be with her, why even bother dating me? Why waste my time? I was heartbroken the rest of the week till he came back and told me he was on a trip with her. I asked him why he couldnt tell me, he said "I knew you would get paranoid and try to stop me from going, so I didn't tell you"
I wanted to scream at him and break up at that second.
I know that he 100% cheated on me because why else would he lie about it? So I told him that I wanted to break up with him because I don't trust him anymore and that he can date her instead but now he is trying to stop me because I have no "proof" that he cheated on me. He apologised about lying but that doesn't make up for the fact that he lied about being with another girl. He is extremely insistent about us staying together and keeps telling me that I am being unreasonable about this decision because I don't have proof of him cheating. What should I do?