Who is this person?

Do you ever have hours, days, weeks, months etc where you are some person that you don't even know? That's me lately. I have been SUCH a brat to people I really really care about lately and I need to stop. It makes me ache inside after it happens. The worst part is that in the moment I don't realize how awful I'm being until right after I do or say something and then the aching starts. I don't get where it's coming from but I need to get to the bottom of this. Anyone have any suggestions? I think I really need to figure out where some of these feelings of frustration and sadness come from that are the starting off point for all of the awfulness. Bleh, I hate feeling this way.