First relationship I need real advice

I’m almost graduating soon, going to be exciting(If I get to at this point lol). But my main focus is my year-and 6 month relationship. My boyfriend is loving and caring, and this is his second relationship. I don’t know if this is just because this is my first serious relationship, but I have serious trust issues with him.

note:this is a very long distance relationship

He’s never cheated on me and never acts toxic towards me, but I always find myself getting bothered by his actions with other females...like I have really bad possessive issues. I don’t actually know if they’re that “bad”...heres n example: I don’t feel comfortable with him being physically playful with other girls, if that possessive? Just my opinion? Is that normal? Am I being immature?

This girl on yt, I saw her talk about her and her man she said she’s fine with him flirting with other girls because he always comes back, like what!?? Isn’t that unloyal by itself? Like I can’t IMAGINE him flirting with another girl, it makes me feel so betrayed.

I don’t know what to do because I can’t help or stop these emotions, but I don’t want to keep getting frustrated with him being around other girls forever he doesn’t deserve that;(

I’m sorry this rant is long but one more thing: how do you create boundaries? Like, when is a red flag a red flag? When is it not? What if it’s borderline?

Sorry so many questions, my main one is how I can feel more comfortable/fine with him and other girls.