Should i trust him?

When he gets back with his ex while getting to know you for the last 7 months...but within those 7 months we were basically together...because it was like love at first sight..but being a male its harder for him to accept his feelings. (Anyways I'm making this story so much shorter so you guys may or may not understand ). While being with me for those months he left me and went back to his ex for 2 months...he then realize i was better for him than he left her. Came running back to me apologizing...i was dumb enough to take him i stupid? Should i trust him? Because while being with me within those 7 months he hid me in the dark, talked to her behind my back thinking i didn't know but i did...never said anything because i was never officially with him...we didn't have that title but basically were a couple.., confronted him about it and he lied to my face about talking to her and not having any feelings for her when he did. They both dated back in the early 2013 then she moved back to her hometown end of 2013...they did long distance guess it didn't work out so she left know being the one that was left is always the one who is hurt and can't let go? Im scared this time around she left him again and that's why he's back with me. He was never honest before i don't know if he's honest now...i also don't like how he still has her on every social media...after i told him if he was to get back with me he has to erase her off everything...i only request that because i don't want them talking again...but yet he never unfriend , delete, erase, nothing of her..should i trust he's fully committed now? Or no? And should i bring up why hasn't he unfriend her off anything? I mean were now officially together ...for a month now ..