Periods and pregnancy

Hi looking for some advice the last two months a have tested an both negitive I am still having a two day period each month however am sick every morning sore breasts heart burn and my stomach is totally changed shape and actually look pregnant however my doctor wasn't so helpful and said a should wait and see was over the phone consultation am so confused and tired i no ppl say some women have periods throughout pregnancy would this be reason tests are negitive thanks this is all new to me