The only thing you can do in this situation is talk to her about it and see how she responds. After that, the next step is to quietly observe, DO NOT pressure or force her into anything. I can assure you over time the truth will come out. One thing to not do is project your past relationship trauma on to your new one, that is just a recipe for disaster. This does not mean you don't exercise wisdom and discretion however, it just means keep your wandering thoughts in check and look for real evidence.

All I can tell you from experience is you have to really make a tough decision and decide if you can actually stay with a woman who keeps male friends in her life(assuming you're a male as well). Some people do it and live "happy marriages" while in many situations those "friendships" become the thing that ruins the relationship. In my opinion it's not worth the trouble or beneficial and my woman feels the same.

Here we go again with the "OP is insecure" comments even though the partner has given reason for suspicion.

He is just a friend OP............Come on now man.

I would be concerned personally and start preparing for the strong possibility he may be already planning to abandon the relationship. There is nothing inherently wrong with having fears however you should know beyond the shadow of a doubt whether you plan to committ to somebody or not.

If he is still debating that in his head that is fine, but before you make any life plans with him and he with you, that part needs to be completely clear in both your minds.