Could I Be Pregnant, I'm scared that its a huge possibility!?

I had about a month ago, and my period two weeks later. I was on the pill but very irregular. I hadn't taken it for two weeks, one due to my period the next just pure carelessness. I had with my boyfriend and he came in me. I figured well I'll start my pills right after, fail, i waited another week and took maybe five total the entire month. I now have been urinating frequently, having lower abdominal cramps, and back cramps, my are a little tender, but not bad enough to have me in a lot of pain, like i barely notice. I get nauseous every night and a headache along with it. That's basically it but I'm scared because my step-mom is questioning if i am. Anyone know?