Quite honestly, I think both of you were traumatized by very toxic relationships. You both were also very young when you experienced these toxic relationships. I think both of you carry deep wounds from what you lived through and it's actually very normal that both of you would genuinely struggle with trust issues and even question your ability to engage in a healthy relationship.

I don't think this guy intentionally lied to you either, instead I think he needed to get to a place in your relationship where he could share more of his history. That's really a scary thing to do too because it can lead to rejection. Also, he probably STILL carries shame for what he experienced and how he handled it all as well.

Both of you should be getting therapy for all the trauma you both experienced. It sounds like you both experience triggers and fears as a result of experiencing these toxic relationships when neither of you had the life skills to deal with what you both experienced. You can't make his history go away, he can't make your history go away either. You both need to heal from the histories you experienced. If you stay together, learn to do your best to develop healthier relationship skills so you can accept whatever each of you failed to know how to handle in your past. You can learn from it and take steps towards building a healthier relationship with each other.