Pregnant? UTI? Something Else?

Okay loves, I have a very odd situation and need some advise. I haven't had a period in 5 months,(Doctors don't know why)...anyways 2 weeks ago my SO ejaculated in me twice. I had pressure on my lower stomach for about a week. I took 3 UTI test from Walmart because I thought it may be a UTI but they all came back negative.I took a pregnancy test today (10-10-17) and it was negative. While I was at work this morning, my coworker had peanuts and I love the smell of it usually but today I couldn't stand it. It made me nauseous. Then out of nowhere my mouth got dry for about 2 minutes and then my Mouth got flooded with saliva. And stayed producing excess saliva for about 20 minutes then went back to normal then happened again 10 minutes later. I ate breakfast this morning and lunch later and 30 minutes after lunch I was starving. Oh and my nipples hurt so bad! Any reason this could be happening?