Me Pregnant? (First Time Posting)

Hello everyone, this is my first post. Please forgive if I dont use abbreviations when needed.
To start off my name is Shannon, I'm 29, and have no children. I've never been pregnant, so I have no idea what it would feel like. My question is...Could I be pregnant or is it all in my head because my period is late and it's causing me to have symptoms? My last period was July 22-26. I slipped up and had sex that started off protected around the 6th of August. I was due to have my period on the 18th of this month and nothing has come. I usually have cramps and sore breast a week before my period but this time I only got the sore breast and they are still sore. Im drinking water like a camel and cannot quench my thirst. I keep spitting like a llama because for some reason my mouth keeps watering. I have a weird taste in my mouth like im chewing foil. Im constantly sleepy, even as I'm typing this! I read that the temp is higher for pregnant women, so I took my temp. and its 99.5. I took 2 pregnancy test, one Thursday and one Saturday and both were negative. Any advice would be appreciated. Thank You :)