just had an affair...

so i recently had this thing happen that's been on my mind a lot. me and my partner of like 7 years have always had pretty open communication about sex stuff, but lately i've just been feeling this weird tension between us. we're both busy with work and everything feels a bit stale. one day at the gym, some hot guy hits on me and before i know it, i'm giving in. we end up hooking up a couple times over the next few weeks. at first it was all just about the excitement of something new, but now i feel so guilty. i know my partner would kill me if they found out and honestly, these moments with this other guy are starting to feel more like a crutch than anything else. doesn't help that he's been dropping hints about maybe moving forward as an actual relationship. what do i even tell him when it inevitably blows up? i just can't shake the feeling that something changed between us.