I read an expert pro-dom who said husbands should never be allowed to masterbate by themselves. You should control all their sexual pleasure. If he goes in the bathroom, he might be thinking of some other woman.
Have you considered tying him up?
Masterbate him a little, then make him swear you are the sexiest! Make him repeat it every which way. Make him lick you until you cum! Then, keep jerking him off until he can't cum any more before you untie him that way he can't fuck you afterwards.
One day, after you tie him up, use a dildo on yourself in front of him. Tease him to keep him excited but don't let him cum until he swears how hot it is! Then, keep jerking him off until he can't cum any more before you untie him that way he can't fuck you afterwards.
Then, sometime, tie him up in the bathroom. Go outside and close the door. Then use the dildo on yourself up against the door moaning and calling out like there's somebody there. When you're done, open the door and he'll probably have cum on the floor! Stand over him and make him lick you while you masterbate him with your foot.
Just keep doing this until he promises you can do anything you want!