coffee dates and late night calls

so i started dating this guy a couple weeks ago and weve been meeting up at the cafe where i work every morning for coffee. it feels so normal but kinda strange too bc its like were just coworkers having casual conversation right? anyway last night he showed up unexpectedly around closing time said hes had an intense day wanted to talk about stuff... things got heated and well u know... we ended up in a back room there wasnt much detail or anything really just kinda rushed feeling i guess? but the weird part is afterwards i was thinking man im still engaged and this doesnt feel right at all but also now its happened idk what to do i should prob tell my fiancee but also i dont want her to think ill cheated or something when it wasnt meant that way. confusing af.