Recently Married

Don't know where to start. I've been with my significant other for 10 years now, but just recently made it "official" a few months ago. We have young kids and by most accounts, we're happy. Don't get me wrong, we're much like every couple in the sense that we're not perfect but we work well with one another. I love him and I thought he was it for me. I have never, not once, looked at another man since I've been with him. The only time we both stepped out of our relationship was when he decided to end things with me (before kids and marriage) because he was seeing someone else and I knew that person. We broke up for a few months. He went his way, and I went mine. Months later, we worked things out and moved back in together and have been together ever since. Just recently, this year someone I knew from high school contacted me on social media, we both followed each other before that and it wasn't like we were all that close in HS, but we knew of each other and he's contacted me before when I was broken up with my husband now...he was going through the same. We talked but nothing came out of that. When he contacted me this one time, we chatted for a few days and I finally asked him, "Why are u contacting me now? I never even thought you saw me in HS." He was a jock and pretty cute but I was a prude back then. And much to my surprise, he said he's always "seen" me. He said that was one of his regrets back then, that he never approached me because he was very attracted to me and now that he's talked to me, he knows we would have been great together. So that's where it started. We've been talking ever since and it's been about 4 months. The more we talk the more we find out that we have in common and just wish things were different, I guess. Instant messaging lead to pictures of ourselves, and has moved to texting and flirting. And we recently decided to meet up. There were sparks! We kissed and it was unlike anything I've felt. Since then, we've continued to text and flirt....sexting. I also forgot to mention he has a son from a previous relationship and a GF (not the sons mom). We have this strong connection...but just recently we saw each other again, only talked and kissed. But this time, things got weird because we both got paranoid about getting caught. I don't want to hurt anyone. I don't want drama, but this is EXACTLY that....drama. I don't know what to do. I feel I should end this before the inevitable happens and we sleep together. I'm feeling so guilty because I feel like I have feelings for this other guy and I don't feel that ending it will change that. How can I just go back to my normal life after this? The seed of doubt has been planted. Help! I'm not a bad person. Am I?