boyfriends ex

i recently found out that my boyfriend has been talking to his ex, he said they’ve been talking for about a month (we’ve been together for 7)

he’s told her about some of the sexual things we’ve done together and gotten some tips off her too

i’m mostly mad at the fact that i found out myself and he didn’t tell me about it, what should i think of this? i have spoken to him about it and he thinks he’s in the wrong for not telling me and i know i’m in the wrong for looking through his phone, so really we’re both in the wrong but what should i do about this situation with his ex?

ps they ended things because she was messing him about and they lived way too far away from each other (la and england)

ps2 she does have a boyfriend but they’re not at their best rn and she wants to end things with him but she can’t or something so wants to move to get away from him

UPDATE i did speak to him calmly and it’s all good, she popped up to him first and i believe that because he has blocked her on everything possible but she got a new phone number and still had his number so messaged him, her new phone number not being blocked, he’s not talking to her now unless she pops up to him again and he’s said he’d be comfortable with me having her number and talking to her myself if needed