I agree with Starr. You very likely are having some temporary blood sugar issues. I did while breastfeeding. Remember, it takes a lot out of you. Eat small healthy snacks or meals frequently & drink up. I used to have cut up fruits & veggies on hand while I was nursing, especially with my twins. I figured for a year they were literally sucking the life out of me. For me, the nausea started around 4ish months, too. I think that was just long enough of a slow down period. I started to feel so good physically that I was doing more and didn't adjust my calorie intake. So the nausea hit pretty hard & fast. Breastfeeding will not affect test results, though, and if you took 3 (spread out a bit I'm guessing?) and all were negative, I'd bet that you are NOT pregnant. Eat. See what happens. By the way, my OB recommended drinking Slim Fast for snacks...it's tasty, has nutrients & is calorie controlled, and is quick & convenient when you're busy or nursing. Good luck!