I was in somewhat a similar situation, I never dated the guy, I wasn't in love with him, but he was always just taking up my time and talking to me, just like how he is to you as you describe. Sometimes, its just best to let go... that's what I did, and he understood that I didn't want him running to me for help all the time. Not sure if this would help, since it sounds like you still care for this guy to some extent, whereas I had no feelings for him at all, buuut for what its worth... hopefully you find the solution soon~
Best of luck.