Heart Torn in Two

I am in a bit of a dilemma and need some advice. I am engaged to my high school sweetheart of 2 years. (I am 19) We plan to get married in 2021. There has been a guy talking to me as well. He is 34, a divorced dad that shares custody, and seems to care about me too. My fianceé has completely adored me over the years, but my heart is in two different places. I have had sex with both. My fianceé knows about one time I was with the other guy when we were separated for a short bit and is ok with me also being friends with him. The other guy has been texting me quite often as well. He has never said he loves me or exactly defined what he wants. He has only been making sure I'm comfortable and happy. I do love my fianceé, but I also love the excitement, adventure, and caringness of the other guy. Any ideas?