Need opinions

So I’ve been dating my boyfriend for going on 6 months now let’s call him Charlie and before him I dated this guy named Miguel so me and Miguel were on and off and he really seemed to just love me for the things I did for him sexually I was the first girl to ever give him a bj and I was in love with him clearly he didn’t feel the same way so I just cut him off and then I met Charlie it took me sooo long to get over Miguel cause like I said he was my first love and I did tent to go back to him so him and Charlie they used to be friends him and miguel and me all go to the same school so as you might suspect we do run into each other and every time I see Miguel he seems to be a little salty and looks at me and Charlie and smiles kinda weirdish especially when I’m alone he will like grin at me and smirk . Before we started dating they were close him and Miguel but when we started dating Miguel stopped talking to Charlie I’ve know Miguel since I was in 7th grade like I said we’ve did things together that were my first he didn’t take my virginity or anything but you know so I’m in 10th rn and my boyfriend is in 11 (he took my virginity) so like I was saying they used to be close but Miguel cut him off .but here’s the thing I don’t see why Miguel would be so salty about us being together it’s not like he wanted me he showed no interest in my besides my body Miguel was my first love and we were on and off again he never really took it serious he always still seems to look at me when I see him I guess what I’m trying to say is why do Y’all think he would be salty after we broke up when he didn’t want me ?