Don't know what to do :/

Hi first time posting just looking for advice/chat I'm a mum to a beautiful boy gave birth in 2012 however my relationship with he's father didn't work out he cheated on me with my sister as you can imagone I was hurt but got over it and moved met someone new who treats me perfect so fast forward 4 years and here we are I want another child and so does he we wanted this for a while now and I feel the time is right however the thought of him cheating and leaving me is holding me back Im scared of history repeating itself I keep telling myself I can't put my life on hold forever has anyone else been in this situation??