I did some very bad🤦🏽‍♀️feel awful

I did so I regret sooo bad last night 🤦🏽‍♀️I had sex with a person that I was badly in love with 4 years ago me an my ex boyfriend broke up a week ago but we still talk cause we have children an we was talking about getting back together I feel bad cause I cried after we had sex cause of my ex Ken I love him so much I just I don’t know I wanna tell him but who knows what he is doing and been doing any advice so I can stop feeling like this an throw this in the past ...I told the other dude how I felt after I was quiet and started crying I don’t wanna be with that man at all I just want to figure my next step with my life with Ken

Any advice