What can I do about the “other woman”

[WellIdontknowwhattocallmyself]

I am 19 and my boyfriend is 22. I don’t want to lose him and we both think we should stay together.
I know the opposite sex can be friends. I have male friends. I am in a serious relationship with my boyfriend. He has a female friend he is particularly close with and has been for years. I am very uncomfortable with the obtrusive things they have shared about themselves and our relationship because I am a very private person. I also unfortunately think she has fancied him for a long time, for various reasons. For example she has given him lovey dovey pet names, is a bit intense and has been sending questionable selfies of herself.
Apparently I have no real evidence that something is going on and I should put it behind me because he wasn’t really engaging in anything himself - until he wanted to go on what was essentially some kind of date involving staying at her place earlier on in the year but couldn’t because her religious mum was obviously against it. I heard from my boyfriend that her own boyfriend who I have never spoken to before thinks I am crazy for thinking she would be interested in my boyfriend

OP you are so young.
Throw this one back. You’ve found out early on that he doesn’t care about making you feel cherished and secure. He’ll get worse.
Goodbye and Next!

Stop doing the Pick Me dance. If you have to fight for him, he’s not worth fighting for. Because if he really loved you, he would put you first. And he’s not doing that.

They have known each other for years. Of they wanted to be together they would be. Apparently both of them have chosen different partners for a reason.