IS BOYFRIEND GAY?

To make a long story short we've been together almost 5 years lived together 2 and half amd these last 2 and half we've lived apart trying to figure us out. Now go back 4 and half years ago i came across some emails between my bf and a man he'd been having sex with and to find out more was he and this man had been seeing one another on and off for 2 years. And two weeks before our first date they'd made future plans and my bf was suppose to introduce this man to his kids and family supposedly to come out of the closet per this man. But he went out on that date with me amd we dated casually for a month and my bf had no contact with this man but the day we decided to be exclusive with one another be committed. My bf spent that day and the next 12 days begging this man to see him but was rejected. Now my bf says that this lifestyle is his past and was trully driven my drugs use. Meth to be exact. But ive come to learn he'd been having sex with men for 6 years before me and a majority of his encounters weren't drug induced but yet him being sober. Now the reason for our separation is due to him cheating while we lived together and since being apart. I have no prove but can only help but feel that not his affairs have been with just women. He swears this past life is just that the past. But i have doubts due to his behavior. Any advice???