Me and my boyfriend have been dating for about a month and he hangs out with A LOT of girls and their always flirty and he talks to girls online too. Every time I ask him if he is he says no and immediately changes the subject or stops talking or pretends not to hear me. What do I do?

If you don't like it, you leave him. It does not get any simpler than that.

Its only been a month and you are suspicious, and he is not forthcoming with reassurance, or explanations. I am betting that's the way he is, and was when you met him. So far all I see is a lack of communications, but if all you are focused on is catching him cheating that's all you will see.

At this stage, ONE MONTH, you are just learning things about each other, and NOT sure what it means. I will admit he is not that open, but maybe he is suspicious of you stopping his harmless flirting on line. Your challenge is to be honest and develop some communications, as that's the basis of trust, and understanding.

Instead of asking is he cheating, or flirty, ask him why he cannot honestly explain himself, and address your questions, and concerns so that you can understand. Maybe explain why you ask, why you are concerned, and why you want to know.

If communication cannot clear the air, don't waste time with some one that you are suspicious of.

Firstly,he stops talking with them because he knows it bothers you. Secondly, just because he is "flirty" and friendly does not mean he cares for you any less. If you accept his open ness with other people, he will respect you more for not stifling who he is .

It's actually good for your relationship if he doesn't jump in the deep end. Those tend to not last as long. Let him flirt and keep old friends; after all, you both need your respective friends to fall back on if it fails. And fail it will if jealousy rules. IF you find real signs of cheating, THEN you tell him you are leaving, clear as that. If he wants to mend his ways, you give him one chance and one only.
It's OK to say that you will give him more leeway to have harmless fun, but if he cheats, you are out the door before he can wipe his cell phone clean. But you'd better mean it.

If you are just dating for a month first why should he not still even date others, relationships don't need to be so serious so fast. Next you learn to trust them, you don't make them prove it.