[M19] and [M24] i feel insecure in the relationship

Me (19M) and my bf (24M) have been in a relationship for 5 month and we have been talking for 8 months now.
I do really love him and I 100% trust that he loves me and cares about me too.
But when it comes to sex, our whole relationship is messy.
At first he asked for an open relationship cause he “didn’t see himself having sex with one person” for the rest of his life. We talked that is a hard boundary for me and i am not okay with open relationships. He agreed to be exclusive with me.
After a month of dating i caught him on dating apps twice. One on Tinder and Once on Grindr. He used his ADHD and dopamine problems as an excuse for Tinder and he said he didn’t talk to anyone there and he said he just used Grindr pfp to jerk off and again he didn’t talk or interact with anyone there.
Whats ridiculous to me is that he didn’t talk to me about being on Grindr after i caught him on Tinder and kept it hidden.
Ever since then i always had a bit of anxiety about him cheating (im not saying he did or ever had the intention but still) he says that he has changed and he is happy to be exclusive with me but i see signs that point to the other way
Its been about 3 or 4 months since then and he deleted both apps and nothing like that has happened again.
But the other i was snooping around on his phone that i saw him text his best friend while he was away on a two week long trip that he would miss having sex with me and he really enjoys that. But the lime after he said “I’m surrounded by so many hot boys here, so tempting”.
After that his best friend asked if we’re open which he said “he is strictly monogamous”.
Or later he texted him that he found it hot that one of his co workers touched him at work.

All of these are signs for me that he is not comfortable with the relationship or he might be hiding something again. Am I overthinking it? Are these types of messages normal between friends when you are in a relationship?