Insecurities, maybe? I need help.

I am rekindling an old relationship. It’s been almost 8 years. We have really talked and hashed things out. Our break up was never so dramatic as I guess others I’ve seen. Things just didn’t work and we knew we needed to cut ties. I was in a relationship after him that caused so much damage for me. After I finally got out of that relationship I pretty much decided I would just stay single and relationships were not for me. Being single for almost 2 years and alone you think hey you’ve figured it out and I’ve done all the self healing but honestly I’ve put myself in a box and I have all these issues coming to surface now that I’m here trying to create the space for a relationship to grow. Even dating in the mean time I always could simply walk away because It was difficult for me to open up and give it even half the energy to really say it was something worth trying. My ex is aware of how bad things got with the last relationship or rather the things I’ve told him and he tried to reassure me but I see me doing little things to self sabotage and it’s annoying even for me. I make jokes about him having little girlfriends and I do feel that it’s insecurities as well as the trust for me and maybe I’m not ready and maybe I should just leave this thing alone before I really ruin it. Because now that things are in motion I feel myself slipping into habits that could make this my last relationship and I don’t want to. Because we’ve been communicating so much about it. Will it get better with time without him feeling so exhausted from having to always go a step above to show me or if he said he would be here and is aware should I just take his word for it?