BF admitted he cheated on both his ex wives

Have been dating my bf about a year, things up till recently had been going great. As i got to know him during the year some things started to seem a little off. His mate, has been cheating on his wife for years, and my bf said that occasionally the mate used His bedroom… when I said I thought that was really weird he said he put a stop to it. Recently I had been getting mixed signals from him… two weeks ago he was reading his emails on his phone, openly not hiding, and I noticed he was getting notifications from a dating website… I asked about it, he told me and showed me he wasn’t subscribed and said he had forgotten about the site (typical ?) but it didn’t sit well with me.

I asked him a week ago if he ever cheated, and he said he’d cheated on both his exes. His reason when I asked was little or no sex in the relationships. I’m very confused about this guy now, should I leave this?? Am I wasting my time?

Oh wow! So let me ask you this... have you already found yourself distancing or shutting down a little? Those are two pretty major red flags to find out about.
Cant tell you what to do here, because a year is quite a while. But I do suggest you have an open conversation with him about these concerns. He needs to reassure you he is not using that dating sight, but why else would he be getting notifications from it? Decide what you are willing to put up with. For me, if I believed my guy was on a dating sight and we were together for a year, Im afraid that would be a deal breaker for me.
Good luck and keep us posted.

He claimed i had "forgotten about it". I have trust issues as it is. The condoning his mates infidelity and admitting that he cheated in the past (though an honest answer) raised more hairs on the back of my neck. He reminded me that i did ask. He answered very factually, never mentioned anything about it being wrong... claims he hasnt been looking for more in websites or using the dating app...

He tried to say something in defense of his mate, to which i said their is no defence, its wrong. I told him that at this will always be in the back of my mind, anytime we are apart, when he goes out on his own or with his mate. I also said that I had yes asked the question, however how i feel about it is not my fault. Im not sure whether to let it sit, or just get out really...

Intuition is real... the hairs standing up on your neck, the feeling you get in your gut, things popping into your head like a little reminder... all of these things are proven to be another one of our God given senses, we just often don't "trust" it.
It sounds like your gut is telling you to get out. There is nothing wrong with waiting until you are absolutely sure that's what you want to do... or not.
Sorry you have to deal with this. Seems as though you know what you want and don't want in a relationship and these things are outside of that.
If you decide to let him go, someone better will come along. If you decide to stay, I think he will have to spend some time proving he is trustworthy to you.

This would make me end the relationship. The fact hes done it twice shows he has not learned a thing and hos matter of fact answer shows that he thinks his behavior was justified or okay. He will do it again. Past behavior is a clear indication of future behavior

Lack of sex is not a reason to cheat. It doesn't make it okay. Intimacy issues are internal problems within the relationship that need to be addressed and dealt with in a healthy manner. Cheating is an external issue where one partner turns away from the marriage and drags a third party into the middle of it. It is an entirely separate issue with far more drastic consequences and nothing justifies it.

This man is either seriously lacking in maturity or emotional intelligence or both and I feel it would be detrimental to stay with him knowing what you know about him

You know never to ask that friend anything about your bf, because they lie for each other. If his morals aren't where yours are might be better to find a guy who matches you more in that department. Also just because someone cheats in the past doesn't always mean they will again but the likelihood is higher especially if they got away with it those past times. Decide what you will and won't tolerate.