How can i forget the past and move on?

I found out my boyfrnd of 2yrs has bn hiding some stuff about himslf from me.He also hurt me deeply when he got emotionally entangled with his ex recently. He says it was coz i cldnt be ther 4 him when he was going thru a crisis n eventually he stoppd believing our relationship was goin to work,tho he couldnt end it coz i was goin thru some problems too n needed him. So we wer living a lie 4a while.We hav sinc decided 2work thngs out bt am so afraid he wil jus hurt me again.How can i learn 2trust again?