Need help i think im pregnant?

ok i had two missed period one neg blood test one neg hpt been having cramps for a couple of weeks now mild cramps have back pains dnt have sore or moring sickness had on 5th of jan what else could it be have to go get sonogram monday and i had to get a nother blood pregnancy test and some blood horomone test what else could it be if im not pregnant i be having some of the symptoms