Pregnant or medical issue?

As of today, my period is 44 days late. I am 2 cycles behind. I have taken 5 different home pregnancy tests, 3 different brands, and they all were negative.
Three weeks ago I was suffering from severe bloating, abdominal cramps, diarrhea, and nausea. My doctor told me I was lactose intolerant.
Since seeing my doctor, I have cut dairy out of my diet. Things were going well and the pain stopped, but still no period.
The last week I have began experiencing nausea through out the day, been light headed to the point of nearly passing out, and food sensativity. 
Could I be suffering from a medical condition? Is my period just more irregular than ever? Is my body reacting to the change in diet? WHAT IS WRONG WITH ME?! Please, please help me..