My boyfriends sexual interests make me feel unwanted. What to do?

So we are in the middle of buying a house together and in November he proposed. He tells me he is in love with me and he is so wonderful.. BUT. He won't stop masturbating over porn at every opportunity he gets, especially at work. He also masturbates over his exes, his best friend (female) and other friends of oura. - I find their pics in among porn and he now openly moans about it as a kink during sex. When we have sex he loses his erection / can't keep erect even with viagra. He claims its from the anti depression meds he took nearly 4 years ago now. Now when we have sex he gets me to dress up as someone else, role play as someone else, talk dirty about his friends, watch porn or generally he never initiates sex with me.. While snuggling in bed he will excuse himself to go toilet so he look at porn and masturbate. He admits he has a problem but won't get help. We tried to quit porn and everything and it just turned into him lying to me (eaislty) and downloading hidden photo apps, vpn, deleting his history etc. (but when I sign into his Porn accounts he's paying for videos on manyvids and got daily activity on spankbang etc). I tried talking to him he just tries to hide it better and lies more. Now I told him I don't care he can do what he wants and we just never have sex any more unless I'm rollplayinf as someone else or we are watching porn. It's so sexually stressful to me. But outside of porn / sex our relationship is 100% amazing. I don't know what to do any more.... I tried being sexual with him when he's at work and it starts off well and then he will say he needs to.. And he will go off to the toilets and masturbate over his ex or his friend or someone at work or porn etc.. Then after he will send me a pic.. And I'm still laid here like, well OK I guess you're not interested in me getting off. I have tried everything from threats to leave, leaving, self-harming, threats to go with someone else, found information on porn addiction, made him a therapy appointment (wouldn't go) etc etc.. I'm lost. What do I do.. I don't know how to get OK with all this.. I have tried masturbating myself but just can't get off as feeling v undesired. I have an average - curvy body with massive boobs and ass and he's just not interested in that. He will openly tell me he wishes I had big boobs like X and when I've searched that porn star has smaller boobs than me!! :/ it's badly effecting my mental health.