PLEASE i NEED SOME GOOD ADVICE PLS?

So..I've been going out with my bf for 1 1/2 yrs..we are very close.. but like any other relationship, we had problems.. and the most imp prob to me is that he loves flirting.. he cannot stop.. he even had secret profiles on the internet to add and talk to girls.. i've confronted him about it. We've ped through difficult moments, and me feeling alone and desperate i've started chatting with this guy.. just friends.. I just wanted to say what i was feeling. he know si have a bf and i really love him.. But now its like he's gone crazy over me, and from my side it was only as friends. i dont really like talking to girls coz i dont trust them muchespecially with bf stuff.. I just wanna cut out this guy from the picture.. He says he wants to go out with me thn he says but im not gonna ruin ur relationship, and its not like i wanna go out with him either. From my side it is clearly friendship and nothing else. What is the best way that I can cut him out and dnt let him ruin my relationshi