Do not trust fiance so should I leave him?

Yup

I would talk to him and tell him exactly how you are feeling, what you are thinking. Tell him if he can’t be honest now, you can’t be with him. See if he is honest about everything after that or if he is still lying. If he is still lying, dump him, he can’t be trusted. If he is honest, just slow things down. You don’t need to jump into marriage yet.

I don’t know if you should leave him, but I certainly wouldn’t marry him until the trust was restored. Marriage is a big step, and it makes no sense to go into it without a strong bond of trust. I think it is your turn to be honest with him and see what you can do about repairing your relationship and the bond of trust between the two of you. If you find that your trust cannot be restored, then perhaps you will have to leave him. Given that you were willing to get engaged to him, however, it is worth trying to work things out before giving up entirely.

^^^^ Read and heed what @SavoirFaire said ^^^^

Yes.

There is nothing wrong with looking at his phone in my opinion. If you need to do it to get your sanity back and believe what you already know, but hope isn’t true, do it. A lying SO will try to deny deny deny, and it will begin to make you feel miserable and crazy. Don’t marry that situation.

Leave him.

Don’t doubt your intuition, we have it for a reason. I have my own intuition here, and I smell a rat. I’m not going to say outright leave him, but definitely pay attention and keep alert here. He’s a gamer it seems, at least from what information you’ve posted about him, and he may be playing another one.

We cannot make the decision for you, because it depends on your own goals and expectations. If you want to have a relationship with someone you can’t trust, because there are other qualities he has that are important to you, that is a choice you can make. You have to then realize that you can not trust him, and let that be part of your life.

Leave for now and demand couples counseling before you will consider getting back together. My bet is, that you are lucky you discovered his true character before the wedding.

I feel like part of the story is missing.

Has he lied about other things before? Have you mentioned that something about this particular woman/friendship makes you uncomfortable? Do you think he’s cheating on you with her?

Since I don’t know you, I can say this and hopefully you can write it off easily if I’m wrong: Sometimes people in relationships become irrationally jealous and controlling. When that happens, it can be easier to just hide a situation than to have to constantly address your partner’s fears about it. I don’t mean to say that’s an ok thing to do, but often enough fault is assigned to one person (the liar) when it really could be shared by both (the liar and the control freak).

I don’t know that that’s happening here. But before deciding to dump this guy, it may be worth examining your relationship dynamic with him, and how you ended up in a place where he is hiding things and lying. If you feel very confident that you’ve handled yourself well, and he’s lying anyway, that is a much bigger mark against him.

Run.

Well, you seem eager to..without talking to him about it…so, to me, it seems clear he’s not the only one with his attention elsewhere.

I think it depends on several things.
Are you easily bothered by him talking to anyone?
What is your idea of borderline?
How long have they been friends? (longer than your relationship or is it new)
Are you unrealistic about his friendships in general? (Do you hate the idea of him having any relationship where you are not included every single moment?)
Has he been unfaithful before?
Is he telling her really personal stuff?
Are there other things that don’t add up that lead you to believe he is cheating?
Did you suddenly get some venereal disease and he says you must’ve got it from some public toilet, but it wasn’t him?
Does he go off to answer calls privately at different hours of the night?
Is he on facebook a lot or some social network and he won’t let you see what he says?
Its hard to say. When I was younger, I knew women who would get jealous if I so much as made their husbands laugh at a joke or if their husbands smiled at me or did some kind gesture for me. I was and still am happily married but that never seemed to enter the equation for them.

That’s an awfully sketchy way to begin a marriage. You might be better off getting out now before it gets rough later on. However, not knowing you or your fiance this could be bad advice. I have a feeling you already know what to do in your heart.

You will have trouble trusting him ever again. I think you have to let him go.

Definitely delay the nuptials until you get this straightened out. From what you’ve said he sounds sketchy.

of course you should talk to him first. the most important thing between a couple is let the other one know what you are thinking about. after your talking, if he is still acting like this, then you can break up with him. just remember, work it on first and then decide.

@akemialmasy How old are you? Do you already have a wedding date?

Slow things down as @chyna suggests. What’s innocent to him is different than to you so you guys need to share your views. If he respects you and wants you to feel prioritized then he won’t give you anything like this to be frustrated by. Maybe he is having an awkward time establishing his personal boundaries and knocking off mild flirtations whether or not they ever went anywhere.

@nikipedia said exactly what I was thinking but struggled to out into words. We can’t automatically assume that he lied because he is cheating on you with this woman. He may have lied simply because he couldn’t be bothered with the backlash that the truth would cause. The question is, do you love this man enough to try and make it work if he is on board too? It definitely sounds like neither of you are ready for marriage but a lie isn’t always cause for a break-up. Sometimes, learning and working on what caused the lie can strengthen a relationship but only if you are both willing to accept some uncomfortable truths about yourselves and the way certain actions makes the other feel/act.