Partner (m30) pressuring (29F) for a threesome

UPDATE: I asked to see his phone today and saw that he has taken a bunch of dick pics he has taken. He says that he was going to send them to me but forgot. And his other excuse was “I wanted to see my dick from different angles”. I’m not that silly 😅

Anyways I think I have gotten the answers I was looking for.

My partner and I have been together for 10 years with kids. We have definitely had ups and downs and for the last year it’s been hard. Our sex life isn’t bad.

A couple of weeks ago he told me he wants to have a threesome, which I have never understood the fantasy of. I explained to him how I don’t think I could and how it all makes me feel. He keeps saying he doesn’t care if it’s MMF or FMM both is a massive turn on. He has been begging and begging me every night for, and actively finding someone (a male) aswell. He has found someone a couple of times online and when I have said no no he has gotten slight mad at me ‘for pulling out’ last minute even tho I never wanted it.

Tonight it’s the same but he decided to look for a female as that’s more his fantasy. As I was asking him questions about it all he started to get worried he wouldn’t perform well and is worried about ‘cumming to fast’ because he’ll ’be fucking some new’

It makes me sad lol I don’t know what I’m looking for with this post or if I’m just venting. I just don’t know what to do. Is a threesome just an excuse to have sex with someone new and not feel guilty? Was he originally finding a male and hoping I would finally agree so I would have to/be okay with a female? I have so many questions I’m lost