Guilty after hookup!

I am a 21 years old and a frequent solo traveller because of which it's common for me to hookup on tour but I have always been sure of making my relationship status clear and talking it out before we do anything about my intentions and that this would be just a hookup , this is exactly how I met my boyfriend 6 months back, I met him on a tour we hooked up during the whole tour of 9 days n eventually started dating since we came from the same cities , he's 12 years elder to me so marriage is around the corner thing for him , so we both have it clear that our relationship would not lead to anything serious so we both are just going with the flow and fulfilling each other's physical need, this time i hookedup with this guy in Delhi , I again spoke about my intentions and told that I have a boyfriend etc. and we did it , while we were on it he got a call n he asked me to be shush for 2 mins i just agreed coz obviously that's what we do when we are hooking up , but then the moment he answered the call he said " yes babe" ..... I was honestly taken aback by this coz I didn't ask him if he was dating or not , later when I asked him about it, he said they are engaged and going to get married next month , this thing is killing me since then it's making me feel so damn guilty that I invited a girls fiance to sleep with me. Idk what to do , and I cannot even stop thinking about it ,