Trouble with a guy and my girlfriend

Hello everyone. I am in a relationship with a girl (im a guy) I go to school with. We are in love, and it is great. We have been going out for a year so far. My best friend who is also a guy seems to be doing things to this relationship I dont like. He used to like her (I think he STILL does, however it might just be my male instinct) a few years ago. My current girlfriend really didnt like him, so they never went out. He asked my current girlfriend if she wanted to date him 2 years ago, and she denied. He acted like he never knew her, and made it seem like she was new to school and acted like he didnt know her at all. Some of the annoying/awkward things he does right now are playing mind games with my girlfriend and me, act completely weird sometimes when both of us are around him, and make awkward sexual jokes with me and my girlfriend in them in some way, and asked my girlfriend, THEN added ME to go to dinner one night (they never did) Ive told him to stop nicely, but it hasnt seemed to work. What should I do? Is there a way to make him stop but still have him as a friend? Im sick of his antics/s**t and want a peaceful relationship. Any feedback is helpful, and thanks.

I don't know if this helps or not but why don't you try to be a bit violent about it (not physically of course). what i mean is that you knew that you friend liked your girlfriend a long time ago right? you have to stop him from making yourself uncomfortable and in case you haven't noticed, if you were troubled by this, then what about your girlfriend? i don't know about her personality but there's a possibility that she feels guilty about her turning him down or something alike since she or you two seem to be fine after all he'd done(indirectly making you uncomfortable). there's also a possibility that he holds a grudge or some kind of malice because you, his friend liked the same girl as him and made her your girlfriend. just try to talk it out with him seriously if he still has some problems with you and your girl. Sometimes you need to sacrifice something to not lose the other or both will be lost. Hope i helped^^