Overthinking?

My husband and I are trying to give our relationship another chance. He had done a lot of things that i am trying hard to forget. Some of it is him flirting with other girls. I stayed for my daughter, at least thats what i told myslelf. A couple of days ago we were out and i went to grab some sauce his food, he forgot to grab it while he watched the baby. When i came back he was talking to a girl. I told him they were out. He didnt hear me at least thats what he said, i said his name, he didnt even take his eyes off of her. There was only the distance of a stroller between us. She heard me and turned to look at me. He first said he didnt hear me and then said he thought i was talking to someone else. So i said well i went to get something for you the least you could of done when i came back was to acknowledge me and ask if i got it. By the way the woman was his coworker.

Im upset. He thinks im over reacting and sees nothing wrong in what he did. Im here thinking if he still flirts when im there how much more does he do when im not. Am i right to think this? What should i do? I dont know if i have the strength to leave this relationship.