Caught In The Act With My Husband's Friend

I met my husband when I was stationed at a military base. We started dating immediately and got married after just six months. Our marriage has been strong, but there’s this one night that haunts me every day. It happened during a deployment. I stayed with some friends on base who offered their spare room. One of them was my husband's friend from his unit, Alex. We’d known him for years and he used to be more than just a buddy; we had our share of flirty moments back then. He came over one evening after getting off work, bringing drinks and snacks. The two of us started chatting like old times, reminiscing about our shared past. It wasn’t long before the tension built up between us again. I remember feeling nervous yet excited when Alex asked me if I could help him with something upstairs. We went into his bedroom and the moment we were alone, things quickly escalated. We kissed passionately, hands exploring each other's bodies. My heart was pounding so hard, I thought it might burst out of my chest. Alex's touch ignited a fire in me that had been smoldering for years. Our clothes fell off rapidly as we made our way to the bed. The sounds of pleasure filled the room as we lost ourselves in each other, forgetting all about loyalty and commitment. It wasn't until I saw my wedding ring glinting under the moonlight on Alex's nightstand that reality crashed down upon me. My body froze and I pulled away from him abruptly, shock written across my face. ‘I can’t do this,’ I whispered. Alex looked at me with regret, knowing he'd crossed a line but unable to take it back now. ‘Sara, I’m sorry… I shouldn't have pushed this far.’ Since then, every time I think about that night or see Alex, guilt eats away at me more than ever before. Am I the asshole for what happened? Should I tell my husband the truth?