I just got out of a Awful relationship with a guy I was with for 2 years and he just dropped and and started DATING this girl 3 years younger than him....guess I wasn’t enough for him

I finally net another guy and it’s been going great but I still have thoughts about my ex boyfriend. The other night I went by his house to drop off some clothes and some kitchen stuff he left at my place..as were talking in my car he tells me how he misses all the things we used to do and I of course missed it too...we started making out and before I knew it....we where in the back seat having sex. I felt so good when it happened I had missed him so much. And now I feel so guilty and bad! And we promised not to tell anybody so I’m telling it here to get it off my chest....