DH has struggled for some time. After some persuasion he saw his GP and was prescribed Viagra which has helped somewhat, but the lack of spontaneity can be an issue (it takes a couple hours to work for him)
We've always been mismatched in terms of sex drive, but in the past have usually managed to compromise well enough. For context, there's no way I could be described as a sexual predator or anything like that, just that my drive is slightly higher than DH's.
Recently things have become worse and DH literally cannot have sex, even with a little help IYSWIM? 
I know it's not his fault but I feel so rejected by it all. I'm aware that nagging or sulking will make the issue worse, but it's so hard not to be upset by it that I struggle to remain impassive.
A similar thread I read a while ago advised that OP to leave her DH as her happiness was so important. I can't even contemplate the upset that would cause both of us, quite aside from the fact that a DH doing just that would be seen as morally abhorrent.
I'm just not sure how I'm supposed to live the rest of my life like this 