I need advice

So my boyfriend broke up with me about 3 weeks ago. We were together 2 years and some months. I guess he just wanted to be single, I don't know. But I didn't talk to him for 2 of those weeks. He texted me out of the blue one day saying he wanted me back and loved me and I was the best thing to ever happen to him and all this stuff. So I started texting him a little bit, and then asked if he wanted to hangout to work through things which he was completely willing to. So last Friday we worked things out and got back together. Well he told me during the whole time we were broken up he didn't hangout with any other girls and was just sad and depressed the whole time. But today I found out he lied, he met up with girls, and also he tried to hook up with multiple girls, WHILE WE were talking about getting back together. So my question is, should I be mad he lied about that? Should I tell him I found out he did? Or should I just let it go?