could I be pregnant??

Okay so I am 1 week past my expected period start date. I've never been very regular, so this isn't unusual. However, I have been cramping and feeling like I'm going to start all week long. I took a pregnancy test on Monday and it was negative. There is definitely a chance that I could be pregnant because my husband and I aren't using any type of contraceptive. Is it possible my test was wrong and this cramping is implantation cramping? It's so hard to be able to tell if my tests can be accurate or not because my period is not regular.