Sometimes I feel very emotional and will cry all day. But, it could also be a reaction to the medication. If it's happening frequently, I would contact your doctor. Some of the anti-depressants and anxiety meds will cause those reactions and need to be changed. Read the labels on your medication or look up side effects on the computer. I had to have one of mine changed because I was so out of control and my emotions were all over the place. I hope this helps.
Another possible cause could be low blood sugar. Have you ever had your blood sugar tested?
I notice the grouch syndrome when I have cheated (though ever so slightly) with some caffeine or too much sugar. We just can't deal with the stimulants normally.