My fiance is dating another lady. Do you think I should still marry him?

Please keep my identity hidden. I am a lady in my late thirties and seriously considering marriage. I met my fiance about three months ago and we clicked. We understood each other and he cared for me very well. We kept a healthy communication and he would always call to check up on me. Sometimes he would visit and buy things for me. But as at then, I noticed something about him, his phone was always ringing and each time I was with him, he would leave his phone on “do not disturb mode.”

When he forgets to put his phone on DND and it rings, he does not take his calls. On the days when I insist he takes his calls, he would do so but in a very reluctant manner. When he answers, he speaks in a very low tone and would even say a few words. He isn’t expressive when he is on the phone. He will always tell the person on the other end of the phone that he is busy and would call back later. 

This happened repeatedly and it heightened my concerns. I became suspicious of him and wanted to find out what was going on. The truth is that I was beginning to love him then and from the way he cared about me, I knew that we were becoming more than just friends. Because I was beginning to have feelings for him, I wanted to know what he was up to and if he had another woman he was dating or wanted to marry. I didn’t want to keep my hopes high or start building something that won’t last. Considering my age, I was too old for games and cruise. 

Because of this, I started monitoring his actions when we are together. I started asking questions and just as expected, he always said it was nothing and the girls that called him were mere friends and nothing more. I told him about how uncomfortable I was about his shady actions and that if we were going to have anything together, he should be honest with me. I later noticed that he changed and the calls reduced. He became better in terms of sincerity and all. 

Later on, he asked me out and we dated for two months before he proposed to me. I loved him and I accepted. However, a month after, I figured out that he was dating another girl. The girl was calling him frequently and he tried so hard to hide it from me. I noticed but I didn’t confront him. I wanted to be sure or even have evidence before I could confront him. 

One day when he was sleeping, I turned on the phone and took the girl’s number. I also went through their chats and took screenshots of them and forwarded them to my phone. While I was going through his chats, I found out that he has been sending a lot of money to her. I was really pissed and confused. The next day, I spoke to him about it and showed him the evidence. He apologized and said that they were dating before we met and he has been trying to end things with her. He said the money he sent to her was to convince her to move on. 

I know all these things are lies but I am confused. He later called the girl in front of me and broke up with her. Even though he has done this, I still don’t know if it’s safe for me to go ahead and marry him. What if he cheats on me after marriage? I like him so much but I don’t know what to do. I need your advice please.