Feelings for someone

So I have been with my partner for 4 years and we have two children. Stuff happens at the beginning of the relationship between both of us and the trust was broken still is. Anyway we don’t do anything together as the children take up all our time together so I feel like we have just drifted and he is only here because of the children he says he isn’t! Anyway I went round a mates house couple of weekends ago and got introduced to this guy who I didn’t think much of at the time. I was told he liked me and that was that. We didn’t speak he text me a couple of tones but also slept with my mate in a hotel. He told me he really likes me and he didn’t even finish with her 🤔🤔🤔 now I feel bad cos I have seen him again and my feelings have got a bit stronger. Am I bad person cos my feelings are drifting towards some one els?? I have never had this is it a crush? Or just a fleeting thing what do I do?