My partner cheated

Hi. Basically me and my partner have been together nearly 3 years and have an 18mnth old daughter. I also have an 8 year old with someone else. My partner is 23 and I am 27. We had a massive row in august this year and I had him removed from our home by the police and he was refusing to leave. He stayed here that night then then next day he came back from work early to collect a tshirt. I had ended our relationship. That night he went out with one of his idiot mates who sleeps with protitutes. They were really drink and my partner took some coke. He told me a week later that he had done it and I exploded I broke my hand on him but couldn't kick him out as I was scared he would go somewhere else. The fing is he said that he only went out with one bloke then that guy said his sister and her friend were there too. His frined got kicked out as he was found doin coke in the loo so they left. His friend was put into a police van for a talk and in the mean time mpartner has apparently met a random girl with a guy who wasn't her bf. He said she said they had some more drugs so he went back to hers with them. He then told me that he didn't do any as she didn't have any so that's another lie. He said that he went to the loo and wen he came out she kissed him and they went to her bedroom and had sex. He said he was wearing his tshirt and that he didn't finish but he doesn't know how long they had sex for before he stopped and said he was going home. In my mind I think that its either one of the girls who was on the night out or he met her in the club and went back with her. I can't keep asking him cause I'm scared he will walk away. He said he doesn't know why he did it but he was angry and hurt, he thought I'd never kick him out of our house. This is driving me crazy I want answers I wana know who where wen how but he gets annoyed and says he can't remember. What do I do? I dnt want to break my family up. I don't think he would do it again as long as we stayed together but I feel really insecure at the moment.

when you okay living with a cheater than why ask him about this,forget this incident and move on