What Causes Hot Flushes, Stomach Cramps And Dizziness?

Im 18, female and recently ive been getting hot flushes, stomach cramps and dizzyness. I had my daughter 61/2 months ago and went on the mirena coil about 3 months ago. Also it feels like ive been feeling little kicks in my stomach. Ive taken a pregnancy test and it came back negative but im still feeling all this stuff. I havent had a period since ive been on the mirena. Could I be pregnant and the test isnt picking it up or is it something else?