Confused about ex-boyfriend?? guys please!?

okk so me and my ex boyfriend broke up in like febuary and we're still good friends. last time i saw him he was like flirting with me a lottt and trying to hold my hand and stuff. i mean it would seem like he likes me again but the thing is HE HAS A GIRLFRIEND! why would he be doing this if he has a girlfriend?? im sooo confused!