Hi, I'm 19 and I am always regular on my period but I have missed to months of my period and have taken three prgancy test and all came back negative. Am I pregnant. I've had no symptoms of pregancy I've never felt healthy then I do now what could this be.

I'd go see your doctor for a checkup. Missing an odd period here or there is not uncommon, but two in a row they would likely do another pregnancy test in office and order a blood test to rule out pregnancy.
There can be a number of reasons for missing periods, it could be you will just have off cycles now and then, but pregnancy should definitely be ruled out first.