What can i do about his controlling behavior?

I'm dating someone who I've dated for 2 years now on & off and he has a really controlling attitude. He questions where I go, who I'm with, he's quick to point out what's wrong with my outfit like if he thinks my shorts r too short.... he knows that I'm not the type of girl who is unfaithful and promiscuous yet he questions my every move still. In the past I've had problems with him flirting with other girls or talking to other girls behind my back. However recently we ve decided to make a new start... yet I'm still bn accused of stupid sh.t like getting with a guy when were only txt buds and hv been cool since BEFORE him nothing more than friends. He always justifies his questioning me by saying I used to do the same thg but the difference was I had REASONING. The stuff he says comes from nowhere. I understand that before (in his case) it was a guilty conscious but (from what he's told me and how they still wanna be with him) he was never this controlling with his ex gfs. Is it bc I allow him to do this? How can I get this to stop? He's NEVER had any reason to believe I was unfaithful! I've talkd to him, etc. Why is he still questioning my every move? I feel like I'm bn monitored! Wth....