I have been gaslighted extremely by my abusive parents. Here's my reasoning regarding this kind of situation: I don't stand to gain anything by "making up" my abuse and "pretending" I have PTSD. It's completely debilitated my life and ruined me. However my abusers stand to gain a lot by denying they did anything wrong. The thing about many abusers is that they actually genuinely don't believe they did much of anything wrong. The guilt of it is too much to bear so they just block it out. Some abusers are open about their natures, others are so lost they actually believe they are good people, like my parents do.

You don't need your abusers to confirm your experiences in order to be validated. In fact I've had several therapists tell me that going to the people that abused me in the first place for help is probably not a smart decision. You know your own feelings. You don't have them for no reason.