Am I pregnant?

So my periods are always irregular. One month it could start on the first of the month and the second it'll start on the last of the month and anywhere in between. So basically every month I have a late period when I could based off of the month prior. I am allergic to latex so my partner and I haven't been using condoms lately. My boobs hurt, I feel nauseous most mornings, and I'm craving foods already. But I took a pregnancy test a few days back and it was negative. I'm trying to wait it out for a bit before I take another one just so it's an accurate read. Advice? Should I just go get a blood test done or should I wait it out and take another one if I don't get my period by December?