Could I possibly be pregnant?

Okay so this is going to be a little long. My boyfriend and I had unprotected sex from December 21st- January 1st almost everyday. I was on the pill. I forgot to take it 1 day but was late most others. I stopped taking my pills January 3rd and had started bleeding the next day. It was red but only lasted for that day. I've been somewhat nauseous, hot at random times, I've had some pretty rough cramps, I've been getting headaches, my moods are out of control and I've been ridiculously tired and I haven't been doing anything. I can cry at the drop of a hat. I took a test yesterday and it came back negative but I feel like it's too early to tell since I don't actually know when my missed period is. I guess I just wanna know if there's a possibility. Thank you!