The guy I am dating sexts and tries to meet up with other girls but still doesn't break up with me. What does it mean?

So I (23F) have been dating this guy (23M) for a year now and I recently found out that he texts random girls on insta and flirts with them and even sexts with some of them. As per some of the chats he has repeatedly asked a couple of the girls to meet up for a movie or just hanging out as well. I don't have proof if he actually met up with these girls or not, just these texts where he insists on meeting them.

And all this while he also expresses affection towards me and behaves as nice as any boyfriend should. If I ever tell him I can't call him because I am busy, he insists on calling me and hearing my voice even if it is for a minute. It doesn't seem performative because sometimes I'm genuinely tired af and can't keep my eyes open and still he calls and we talk for a few minutes. So I don't think he is faking that much of his feelings for me.

I am so confused because it seems to me that I had a picture perfect relationship but apparently not. But if he is getting so much attention from all these girls then why not just break up with me and pick one of them and give them all of his attention.

The only reason I can think of why he is doing it is because he finds me unattractive and to be fair the girls that he texts are very stunning. I'm not an insecure person but what I mean is that objectively speaking I am nowhere nearly are beautiful as them physically. So perhaps it is only because of lust.

But I still don't understand why he simply doesn't want to break up with me because even for me physical attraction is important. So why don't guys just choose women who are their type?

I'm racking my brain as to why he isn't simply leaving me...