The boyfriend who cheated on me and we played a quadrangle love game

I am 22 years old, a student who will graduate this year. My boyfriend is 25, my senior in college, and he has been working for two years after graduation.

Maybe it's because we are in a long-distance relationship, so he always encounters flirtations with other women. After we were together for only a month, I found out that he had a "sister" C. I thought that since we just started dating, there might be some personal emotional issues he hadn't handled properly yet. So, I explained my attitude towards our relationship to him and hoped that he could resolve these issues as soon as possible.

After the C incident settled down for a while, less than two weeks later, he met another woman called Sister D. At that time, I was both angry and amused. He came to me like a little kid, apologized, and promised to handle the situation well. I believed him and didn't worry too much.

However, later during the National Day holiday, when I went to visit him, a girl suddenly called him at midnight and said, "I miss you." At that moment, my heart tightened, and I realized the seriousness of the situation. I remembered that we had been having a lot of conflicts recently. He was always criticizing me here and there, not calling me, and saying he was busy all the time. Whenever I tried to subtly ask him about it, he always lied. I thought maybe I was being too unreasonable and had done something wrong. Now the truth was revealed, and I felt a bit disgusted by him. Later, he cried and begged me for forgiveness, saying that nothing had happened, and he only regarded her as a sister. He said he just shared his inner thoughts with her, she understood him, and they enjoyed being together. He also said that it was because of the distance between us that caused this; if we weren't so far apart, he would have stayed by my side peacefully.

Although we reconciled after this incident, there was a thorn in my heart. I couldn't think carefully about the lies he told before, or I would feel upset inside. I just wanted to ask him, what was he thinking at that time? Am I really that bad? If we're not suitable for each other, why force ourselves to stay together?