Sleeping and hitting problems, have you tried this?
As far as sleep goes, If you want to go the route of benadryl, etc... then I would try a cup of chamomile tea or a Hylands teething tablet or two (even if she is not teething) first. Benadryl might have the opposite effect of calming, and it has all those artificial colors and stuff. Also since you are still nursing, you might try to cut out things out of your diet that she might have sensitivities to, like dairy.
As far as hitting, we are going through that right now. What we are trying now is instead of saying "No Hitting" (or kicking or throwing, etc...) we say thing like "Be Gentle" or "Love on your mommy" if she is hitting me. Our logic is the first thing you think about if I say "Don't think of an apple" is probably a big red shiny apple. So we are hoping by not repeating the bad behavior with words, we are making her think of something else. We are not sure if this technique is going to work for us, but we are giving it a try.
I hope it helps, but hang in there, I have bad days too, when all I want to do is hide in the bathroom for a few hours, or at least say breastfeeding is off limits(my toddler nurses at least five times a day and wakes up twice a night, and I also have a 5 month old who, of course, nurses a lot as well.) I think all mothers have bad days

It doesn't mean we love our children any less, or that are failures as good mothers. We all just need some more sleep!