Why couldn't I stop being with this person?

I've been in a relationship with my now-fiancé since 2019. We had a rocky start to our journey. The feelings were mainly on my side; he chose to be with me because he feared he could never get a similar amount of love or more from someone else. I stayed by his side always, sacrificing my chance of being truly loved for these five years. Last year, during our long-distance relationship, he explored other options but did not find anyone who was wife material or matched his and his family's values. After our engagement, I later found out that he kissed a girl on their second date. He did all this while I was at my lowest point in life. A few months ago, I asked him why he didn't go along with that girl and why he came back to me despite having feelings for her. He said it was because she did not show as much love and concern as I did. He never cared about my feelings. He wants me around and is marrying me only because I love and care for him a lot and will never leave him, as I promised at the beginning of the relationship, and because of my moral values. I hoped he would grow some romantic love for me over the years, but now, as I stand, I am marrying a person who doesn't love me back, who is just here with me for his selfish reasons or because he couldn't find anyone better. Whenever I express my concerns, I am told that there's nothing wrong with me and that I am getting what I want: marrying the person I love. What more could someone ask for? Why couldn't I stop being with this person all this time despite all the suffering and emotional turmoil he put me through?