What Causes Bad Breath Along With Diarrhoea And Nausea?

About a week ago i have had signs of bad breath, diarhea, and nausea. I was in a relationship from the end of November 2014 to the end of december 2014. I was tested for hiv about a month or 2 before my relationship and it was negative. I tested on February 5 again and it came back positive but a faint line. i havent been with anyone else and my ex says that he tested the end of november and was negative. How could I be positive and he be negative? Something isn't adding up and I'm freaking out. I think he is lying about everything. Can another health issue cause a positive hiv blood test? PLEASE HELP