Is it possible for me to be pregnant?

I have been on birth control for almost 5 years, missing a pill only every once in awhile. I missed a pill sometime last month, but followed the directions for missing a pill. I had unprotected sex the last day of my blue active pills but I still got my period. It started Tuesday night and was off and on and a little lighter than usual. It's usually over by Sunday but I had not bled all day Saturday and my boyfriend and I had unprotected sex again that night. Sunday morning I had been spotting and have since been ridiculously tired. Today is the first day I have not been super bloated. I have had cramps which is unusual for me to have this soon after a period and occasional sharp pains in my left side, lower back has been cramping, I've been rather irritable and emotional and food has been tasting a lot less good. I've also been getting headaches almost every night and I very rarely get them. I thought I was getting a cold but it has gone away and I've also recently quit taking some diet pills, so maybe the headaches are from caffeine withdrawals but I tried taking one the other day and still took a nap immediately after work. Is it possible for me to be pregnant?