Unfortunately men aren't like computers and we can't Ctrl+Alt+Del their dating history or restart them when they aren't working properly. You can't make him forget his ex and you can't control what girls contact him. If girls are constantly reaching out to him whether it's as a friend or more, like you, they've also realized that he's a catch and that's something to be proud of! Remember, he chose you honey!
We've all been that obsessive girlfriend, stalking the social media accounts of every girl even likes our boyfriend's status. And we've all been that single lady on the prowl, disregarding another girl's feelings. But how do you dismiss these feelings and thoughts that reek of insane jealousy?
First, figure out if this is even an issue between you and your beau. Do you blow things out of proportion in your mind? Or is this a something that genuinely makes you feel uncomfortable?
If you're not just being an insecure control freak (which we all are sometimes, girl don't trip) then the next step is mapping out the relationship your man has with the girl(s) in question. Is this a two-way street? Is he engaging in flirtatious messages with her? Or does he shake it off and respond in a cordial but appropriate manner?
Make sure you're not going to make a mountain out of a molehill if you decide it's something you need to confront. In a mature relationship, you have to address things without crazy eyes, yelling or tears. Be honest with your man, tell him you don't like when he talks to her. If he replies with a mildly sarcastic retort about how you're overreacting and that they're "just friends" then let it go in that moment. If he's belittling your feelings, he might be hiding something. An upstanding guy is going to respect you and be open to a dialogue about how he can prevent making you feel uncomfortable. Wait until there's an occurrence and point out how inappropriate their interaction is.
If you come to the realization that the problem is with yourself. You need to give yourself a big hug and realize what a fucking catch YOU are. Who cares about the girls he's dated in the past? There's a reason that he's no longer with those girls and that he's with you. Let it go, laugh it off and give him one more reason to be with you. No one wants to be in a relationship with someone who's insecure and constantly needs reassurance. Stop focusing on how crazy these girls make you and start focusing on how amazing he makes you feel.