Pregnant?

So I'm pretty sure I had an abnormal period now that I think about it from Dec 22-26, first day bled then spotted then on. My boobs were tender the a day or two the following week. Now, I'm getting cramps coming in waves and I feel "full" lately. My back has been sore too. My boyfriend and I were intimate on the 6th, 20th, 27th, & 31st. Any ideas? Took a test midday today and it was negative.