Regret/doubtful/hormones? Help me figure it out PLEASE or at least understand it.

So I am 26weeks pregnant about 6months with my second child. My first child is a 4 years old girl. This one in the oven is a boy my 4year old I had with my ex husband. This one is with my current boyfriend. I’m having doubts being with my boyfriend I’m a Sagittarius I’m not sure if that has anything to do with it because we get bored in relationships very quick if it doesn’t stay spicy etc.. but I had a dream last night that I texted my ex husband apologizing to him for leaving him and I wanted to get back with him. I do not like to regret anything in my life. But this is the first time I’m really regretting leaving him or doubting myself but it could be hormones from the pregnancy. Im just really confused. When I divorced my ex husband I’m not 100% that he cheated in me but he stayed at his ex girlfriends house for three days because him and his friends got in an argument when he was living with them when we were trying to see if we can work things out we needed out space for a bit. But instead of him calling me to see if he can say at home for a day or two to let things cool down at his friends place he goes to his ex girlfriends house. Im sorry there is no way in hell for three days he didn’t anything with her and plus I had to call her phone number to get ahold of him. So that just pushed me to getting a divorce. But I’m thinking back on it that he probably was telling me the truth and never didn’t anything with her. Long story short lol but I think I’m still in love with him. And not really in love with my boyfriend that I’m having a baby with. Im confused and scared to say anything to either my brother or ex husband. Anyone ever been in my shoes? Send help pleaseee or understanding