Had a big row over him looking at a bar girl?

I as out with my partner we are both 35 and we were in a pub at the bar. I turned round to talk to him at the bar and he was looking a young bar girl up and down in front of us and didnt even hear me. I was so mad at him that I told him it is disrespectful when he is out with me. He said he wasnt looking at her ually just happened to notice her and I am total over reacting. I just felt like rubbish for the rest of the day. Im not usually a jealous person but when he is out with my I dont expect to catch him looking a very attractive young woman up and down right in front of me. Am I wrong to feel like this. He has said he wont do it again but he has done this a few times over the last few months and its making me not want to go out with him anymore..... He is loving and attentive and we are really happy together so why does this have to spoil things. He is not a flirt and so I cant understand where this is coming from. I look after myself and am consdidered attractive so why does this bother me so much and why do I feel it is rude manners. I know I shouldnt have got angry and it ruined the day but is there anything I can do to help things?