What Causes Light Period Bleeding With Mood Swings?

ever since march 6 of this year, my boyfriend and i have been having sex. we dont use protection and he doesnt pull out. i had my period on the 15 of march, but it was alot lighter than usual and it only lasted 3 days. i have been feeling really tired, lately and everything i do, i get worn out easily. i also am gaining weight in my face and belly. and i have mood swings like crazy. i also have been eating things that i usually hate to eat. could i be pregnant?