My SO and I have sex pretty regularly and my cycle is generally predictable but this month its been different. I had heartburn for 3 days straight after ovulation, I've been extremely tired, I've been nauseas almost every day for the last week, I've had sharp cramping, and generally my boobs are sore about a week before I start my period but they aren't this month. My period isn't for at least another 5 days, and I took 2 tests a couple days ago but they both came up negative (obviously it was too soon). How likely is it that I'm pregnant? Could I just have a lot of random symptoms piled together?

HELP!