Random mood swings?

Aris

Today was my bf birthday and it was a great day of course but later on I started feeling annoyed and sad for no reason I think its cause im tired but anyways there is alot of days where I get those crazy mood swings where im fine, then i fall quiet and sad for no reason thrn go back to being fine. It can get very annoying. Anyways we were at dinner and since I starred my period yesterday I wadnt hungry at all and I kept insisting I wasnt and I was fine, so through dinner I kept zoning out and i kept trying ti pay attention t the converdation but I just zoned out, I looked pissed and annoyed which I had no intention of doing but I cant hide my emotions and im expressive with my face and I really had no intention in showing it but I did and it sucked, I later felt better when I was alone for a few minutes and I was back to normal, my boyfriend took me home and then he had a moment and it was quiet the whole ride and I tried getting him to talk and make sure he was okay and he said he was just having a moment and I honestly feel like maybe I was sometype of selfish??? And I know i probably was rude but i really didnt mean it. I feel like i ruined his day maybe and i feel bad annd I said sorry to him alot but I have no idea as in why i have these mood swings and why they effect me so much. Also if someone has tips on how to surpress emotions please tell