What Causes Hot Flashes And Hollow Feeling In Stomach?

I am 30 years old. My periods used to be regular with a 31 day cycle. The became irregular after my 1st child at 21. Ranging from 28-52 days, but 9/12 mths a year 31-33. I have been trying to conceive for a year now. My LMP was April 4th. I have been have hot flashes and this hollow feeling in my stomach. I took a pregnancy test on May 3rd, which would have been cycle day 30 but it was negative. Is it possible that I maybe perimenopausal?