You asked and I'm afraid, in manspeak, when a woman 'asks' we usually translate this as 'you better do this now or I'll not shut up about it for hours'. Its the same reaction to comments like 'Oh, you are thinking of wearing that shirt?' which obviously means 'I hate that shirt with a passion, it makes you look fat and the colour clashes with my handbag. Take it off and put on one of the approved shirts or else.'
You may not be aware of this, but this is how men interpret 'womanspeak' a lot of the time. You may not even have intended this intepretation but it is something that is ingrained into the male psyche. The trouble is that men also often respond to this strategy with reluctance - we do what you want because we know we'll never hear the end of it (even if that is not the case, we are talking irrational ingrained responses here...) but we don't have to like it.
Plus, ask yourself this... say you were not in the mood for BDSM and he was. How would you feel if he demanded BDSM? Ok, as a sub you may feel obliged and even happy to obey his orders but probably not as much as if you were 'in the mood'. In order to 'do the job properly' you both have to be in the mood otherwise you will end up with a half arsed effort that feels lacklustre.
Maybe what you, as a sub, need to start doing is thinking about his needs more practically. If you want him to perform, make sure he is relaxed and ready for action. Rather than asking to be tied, try to make the evening on which you want bondage to be as relaxing as possible - make him a nice dinner, offer him a massage, make sure that you are there for him to do with as he wills. The service may help waylay your own feelings from a bad day and, if you make him happy enough, he may oblige with some bondage.