Why am I acting like this ? :(

So the past 2 days I've been such a bitch to my boyfriend. I've been stressing and worrying so much about the smallest and stupidest things and I've been giving him all the hell and having the worst mood swings but my period isn't suppose to start until another week or so. All my boyfriend has done was try to be here for me but I'm being such a bitch to him. He's asleep right now but it just hit me and I feel terrible. Why am I being like this? Has any other girl had this problem? What can I do to make it up to him? I really do love him and I have no idea why I'm being this way towards him. He's the best thing that's ever happened to me... :/