sex has died

[Anonymous]

Been with my partner for a year now. To start with things were fab. We always got along, had sex daily and generally had a healthy relationship.
obviously in all relationships the sex dies down naturally.
However. ..its been a whole month now and despite my efforts he just will not have any sort of sex with me.
The last time we did I bottomed for him and its not something I do often. We have spoke about roles etc and he prefers to be bottom and I prefer top. So I have tried coming onto him as a top and still nothing.
We keep having silly arguments about non relevant things and sometimes it turns into a big argument where he threatens to leave me or vice versa.

Now...my worry is that he may be getting it else where. I have asked him but he tells me not to be daft etc.
Also...he says he isn't horny. But a month not being horny seems a little stretched to me. Considering his normal high sex drive.
He also masturbates and when he does I have tried to come onto him then too. But he still doesn't.
Now im really worried he either isn't attracted to me any more OR he is getting it somewhere else.

I know there could be many reasons why. But... I would like some opinions.
Have you had anything similar happen to you or could you offer me advice on what steps to take?
I have tried the talking approach and I get alot of negative response. He accuses me of only wanting him for sex and it starts arguments again.
Talking doesn't work lol. Even in the calmest manor he seems to think im starting on him.
So....HELP plzzzzz