you're going to have periods like that from time to time.
drawing can be fun, but it's work. and sometimes work isn't fun.
trying to fight it or forcing it is useless. Also blaming or being mad on yourself.
no one can create feeling like that, and trying too hard to do something just put
too much pressure to actually succeed in what you try to do.
From my experience, Try to take the entire day off. do some other things, whatever you like. it will make you feel a little better and who knows? maybe you'll get inspiration from something.
You can try to get back to this little by little, after that day.
(try not to take too much break from it, like 2 weeks or so. the reason is that I think it might make the whole thins into a monster you'll be afraid to confront, and you'll just want to avoid).
One last thing, maybe the most important one actually...What do you feel when you usually draw.
do you enjoy it? do you love what you're doing? you think you're making good art?
sometimes we may be too judgemental toward our creations that it blocks us from create because we don't think we good enough. If you feel that, maybe find ways you can improve. it's always a good idea anyway, there's always room for being better 
Hope that's not too long, and somewhat helpful.
