Is it normal to be jealous?

I'm fwb with this guy and whenever I see him with other girls I get jealous. He was my first so i think that has a little bit to do with it cause I feel more kinda attached or comfortable not sure how to put it. We have been fwb for over a year now and have knew each other since we were kids. And the closer we got the more and more I started to like him. I feel so guilty when I get jealous tho like i shouldn't be jealous I should be happy for him. But anyways... Is it normal to feel jealous like that? Any advice on how to get over it? Thank you ladies in advice! :)