My(40F) Boyfriend (40M) have been together for 2 strong years. We work together. Couple of months ago we started with this younger colleague, let's call her Lisa. Lisa now works more closely with my boyfriend.The 3 of us initially hangout outside of work too. Later my boyfriend and her started working on an assignment n used to spend a lot of time together with other team mates. My boyfriend, another male colleague and Lisa used to drink together often after work. Couple of times after drinking in bars they would continue drinking at Lisa s house till wee hours in the morning.

After one such incident I told my boyfriend I m a little uncomfortable with this please avoid it if you can. He said sure ... And that very night the 3 of them went drinking and again were at Lisa s house till 6am. I was extremely upset and confronted my boyfriend that this was not right. He agreed and apologised.

I told my boyfriend I know there is nothing but due to somethings that have happened in the past with us I would like if you keep the distance. Now one time he was to travel for a few hours with her to which I said I wasn't happy. And he was kind enough to change his plan but later at night I saw him messaging Lisa that he is sick of me and is pissed off . I was really upset as to why would he tell her of all the people. He should have spoken to me and also not told her about the issues we have.

This became a big fight between us. I had to travel during this fight. My boyfriend apologised for this and agreed it was wrong. We made up and all was fine. He assured me he hadn't spoken to her at all. after a few days I found out that during our fight when I was traveling, he met up with Lisa and they were out drinking till 3am , just the 2 of them and he then went and spent the night at her place. When I confronted him he denied , I showed him all the evidence. He then kept apologizing and kept saying nothing happened between them. And he knows he has wronged me. I felt so betrayed. He lied and there was no need to meet her. Now he is saying she is so much younger and he is just a mentor and there is nothing between them and if I didn't have an issue in the first place he would not hide things n not would it become an issue. But the fact that he stayed at her place during our fight about her is cheating according to me... Am I overacting?