What Causes Delayed Periods And Vaginal Spotting?

Hi I am a 43 year old woman, and my period is 3 weeks late. It has always been extremely regular up until now. I took 2 home pregnancy tests and one blood test at the doctor and all were negative. I had a couple of days of light spotting about a week after my period was due, definitely not an actual period. I have also been getting hot flashes at night the last couple of days, which usually happens before my period. I m also just generally not feeling like myself. Could this be perimenopause?