Love Triangle

So there is a cancer guy I have been talking to - it seemed like he was really interested but there were tons of mixed signals! Mainly on my part and my friend who was telling him i had no interest in him - he is also VERY insecure. I have a lot of male friends and guys flirting with me a lot and I could see it was bothering him. Anyways, now he started dating some girl he met 2 weeks ago yet he is still contacting me asking me to hang out. I met her once and all she did was freak out and feel threatened by me (she could tell he liked me) to the point that she threatened to leave and also insulted me. Why would he ask me to hang out with him and his gf if I like him? Either he is cruel or doesn't think i like him! Obviously I don't want to hang out with him and his"gf"- Is there a polite civil way to handle this?

"Is there a polite civil way to handle this?"
Uhhhh ...say no THANK YOU. ?
Because if he's asking you to hang out with him and his g/f (but he does like you), he's obviously not serious about his g/f (if he is interested in you)... but I don't see how he would figure, him showing you the way he treats his g/f is supposed to make you want him if that is the case. He has a girl, if he doesn't respect her... that's not the kind of guy you want anyway... RIGHT!?!?!?

well, for 1. i don'tthink he thinks i like him and 2. I think he is dating her just cuz she is "easy" - typical guy.

In that case, I don't think you're his type... as far as relationship material is concerned.
If he's after her cause she's easy (unless he's just trying to 'hit,' which should still turn you off), just the cusp you're on (mentally post-it noting everything with indecision LOL j/k) tells me that you're not. Personally, I like a woman who can do everything on her own (...but needs a little help emotionally [I love to take care of my partner that way]).
Aside from that, I would have to say, if he's not trying to get your attention that way, he does like you as a friend. I will also add, that he probably wouldn't appreciate you trying to break up his current situation for your own benefit (not saying that you had plans to).