Is he trustworthy?

I posted this before but I’m posting again because it’s getting worse and it’s really ruining my self esteem and my confidence in my relationship . My fiancé and I have been together for almost two years, we have a baby on the way. I’m 24 weeks pregnant. Since a few months ago I’ve been noticing he’s been staring at other women. But it’s gotten so much worse lately. These women in my opinion are average women nothing special. My fiancé has literally been turning his head and doing double, even triple takes at women that I find to be average. I truly don’t look at other men or think about other men. I just don’t care to. Is that not normal? I confronted him and of course he denied it but he was very sweet to me after which showed me he felt bad. Yet he still does it? I’m feeling like he’s really thinking about every woman except for me at this point. I wanna get on his level and just gawk at a man right in front of him just to show him how it feels cause I know he’d hate it. Is that immature of me? If he has that little self control when he’s with me can I actually trust him? Because it’s literally making me second guess marriage.