Can't get away from his ex!

Ok so I've been going out with my boyfriend for just over 5 months now and I'm starting to suddenly feel a little insecure in the relationship due to his online friendships with other girls(especially his past lovers/flings). I don't mind him talking to other girls, the only thing that bothers me is that some of these girls actually like him in a more than friend way, and he knows it too yet he seems to enjoy talking to them. I told him not to talk to them but he still does it anyway. There is one girl I really don't like him talking to, his ex( his first girlfriend and first love). I don't like her at all, I personally think she's just very fake and I feel like she may have feelings for him. She is the main reason we fight sometimes. Every time he's had a little bit too much to drink he gets extremely jealous of his male friends when I chat to them. Its because his ex left him for one of his friends and for reason he thinks I'll do the same to him! I keep telling him I'm not her, I won't do that because I love him so much. This makes me feel like he's not over her or what she did to him. Am I right or just paranoid? Also she recently broke up with her boyfriend of 2 months and immediately started chatting to my boyfriend... He told me about this and I asked please not to talk to her again. I know its a lot to ask of him because they are in the same group of friends. He told me not to worry about her, he said she's not a threat to me. I really want to believe this. I trust him completely.. but I do not trust her. I'm afraid if he spends time talking to her he may start getting strong feelings for her again. He now knows that I really don't want him talking to her, so now he has started lying to me about it. I was on the phone to him while were both on facebook and I asked him who he was chatting to. He said he was talking to his friend james but the next day when I was with him he left his facebook on and I saw that he was not talking to james, he was actually talking to her. I didn't say it to him because I don't want him to be mad at me for snooping through his messages(which I know was wrong) I just don't understand why he lied? He tells me he loves me all the time, and I believe him. But if he really cares about me why can't he just not talk to her like asked? I don't talk to any of my ex lovers because I know he would hate that. Basically what I really want to know is am I wrong for thinking he might have some feelings for still... and always have feelings for her? I feel like I'm second best. What should I do?

It doesn't really sound like you truly trust him then. If you do, I would let him talk to who he wants. Even if the other person likes him, if he's actually trustworthy, he'll stay true to you, so it shouldn't even matter. I understand your concerns, because you can never know for sure. But, if anything does end up happening between them, then he's not right for you anyway. Because someone who actually cares about you and loves you wouldn't cheat on you. Why do you feel like second best? Is he hanging out with them or talking to them more than you? Or just because he lied about who he was talking to? He probably lied because he didn't want to upset you, but he also doesn't want to give up friends just because of you. I don't think he should have lied to you, but I also don't think you should tell him who he is and isn't allowed to talk to. So, I would allow him to have his friends, even if they are exes. If you really trust him (even if you don't trust her), then I wouldn't worry about it. But just keep an eye out if there's anything more. If he lies about what they talk about, then that's when you should be concerned. Make sure you keep maintain good communication and honesty, or your relationship may really be in trouble.