Lifestyle tips

I'm not sure how to help but I'm a transgender lesbian, but I'd just tell him that it makes you feel like you aren't enough for him maybe? I'm not the best at advise but I at least want to help a little if I can 😸.

I'd say if they're friends and you know it, it's completely normal otherwise I'd be careful.

He also shouldn't do it right in front of you that's just cruel.

I don't think it's at all unusual, even for men who love and are attracted to their partners, to look at pictures of other women. I do think it's disrespectful and inappropriate for him to be doing it in your presence, especially since you've voices your feelings.
All of this aside, please don't feel inadequate. You're not. You have every right to be treated with kindness and respect. If this relationship doesn't succeed for whatever reason, you will find love again. I'm not saying you should dump him over this, but don't settle for less than you deserve.

Looking at others when he's right next to you is quite a big no-no in my book, especially if he knows how it's making you feel.

No, that's weird. Sorry. I mean, no one's normal, including me obviously lol, but that is a different kind of strange. I'd guess it to be one of a few things, some of the likelier of which, imho, are:
1. He is trying to get you to do it with him, for any of several reasons, possibly not even thought out..
2. He is trying to manipulate you or your feelings, again for any of several reasons.
3. He doesn't know how to be in a relationship yet and is still testing what is appropriate or acceptable.
4. (Similar to 3) He is testing you or himself.
5. He is socially retarded.