Your fiancé looking back at another woman

My fiancé was picking me up from work yesterday night , and he told he had seen his ex on his way of picking me up and I said oh okay . On our way back home he tells me where he saw her, he's still driving and turns back to see if she was still there.. Am I wrong to be mad at this?? I'm irritated .. He said he turned back 5 other times and I didn't get mad at those times.. I need advices . Am I just over reacting, lately I've been getting mad at these stuff and he makes me feel as if I'm always  wrong ..