Relationships

So I was on my boyfriends phone the other day, we always just go on each other’s phone no big deal. But this time he got a message from another girl, and ten second he saw it pop up he took his phone back and didn’t let me touch it for the rest of the night. I asked him about her and he said that she is just a friend and that I should t have to ask cause I talk to my best friend whom is a guy all the time.

I want to trust him but like I feel like he is keeping something from me.

He also seems to text her ALOT when I am with him and when i am not with him he never responds to anything I say until hours later and it’s usually a really blunt answer.

Any tips on what I should do??