Why is he being like this?

[JanuarySunshine88]

Been with my partner 10 years and have a 5 year old and a 4 month old. I've had a shit few years with bereavements and I had a difficult pregnancy. He wasn't very supportive and just made me feel like I was a nuisance. We argue a lot. I think he's slept in bed 3 times in the past 6 months or so.
He tested positive so I've temporarily moved out with the kids.
He only talks to me if it's about sex. I used to sleep around a bit in my 20s and he keeps saying he wants to get the "wild me" back, asks what I did with my ex's and what sex was like with them? Where I've had sex and says it turns him on. He says the lack of sex is part of our problem. He's obsessed with the idea of a threesome. I only go along with it cos it's the only time he'll show me any affection or compliment me. Its like he wants to show me off and gets turned on by the thought other people find me attractive.
The "wild me" is dead. I'm not her anymore. I'm a mother of 2 and I'm now tee total. But he's obsessed that she's "still in there"
Then in the next breath he'll be saying he wants us to split up and wants my name off the mortgage and me to go back to his parents. He tells his family about all our arguments so they all hate me.
Can anyone analyse this?

Stay away from him; he doesn’t sound like he loves you or appreciates you or supports you

Luckily you aren't married to him! Why doesn't he go and live with parents and take his name off the mortgage? He's obsessed with sex, he hasn't any regard for you, he's no use to man nor beast so just get rid OP.

I lost my job through COVID and it was only part time anyway so I couldn't afford the house on my own where as he can.

What’s there to analyse? You need to put your kids first and separate. This isn’t a partnership or a family for kids to grow up in.
Why did you think it was a good idea to bring another baby into it?

Short answer. He's abusive. Get rid. Otherwise he'll leave you in a few years himself.

That's like saying 'My house is on fire; help me analyse the flames.' whilst your most beloved possessions are inside.

You don't need it analysing, you need to understand that if someone makes you feel crap, you need to stay away from them, not analyse the crapness. People are rubbish for millions of reasons, and sometimes a whole mess of reasons, changing all the time. You'll never work it out.

Spend time with people who don't make you feel that stuff needs analysing. Don't spend time with people who do make you feel that stuff needs analysing. That's boundaries and self respect, in 2 sentences. Don't try to complicate it with analysis; it's a massive waste of energy, and even if you got the answer as to why he does it, it wouldn't stop it from ruining your life, would it.

I agree with PP. This relationship is not making you happy, it's clearly not making your partner happy and it doesn't sound like your partner actually wants to try and repair matters.

Get some advice about what your finances would be if you split. Though you're not married your partner would have to pay maintenance for the children to keep a roof over their heads. Don't feel like you have to stay as you are because of the financial hold he has over you. And definitely don't have a threesome to try to please him or "win" him back.