She wants to marry a HIV+ man

I am a guy aged 35 living and working in Nairobi. In 1998, I dated this lady who bore me a baby boy. When she joined university, we parted ways due to peer influence on her side and because I was not financially able to care for her and the child. She later got pregnant by another man and gave birth to a girl. We met in 2007 and she explained her tribulations in the hands of this man. I wanted to help her but we lost touch again till February, last year. We started dating and were even planning to get married. I had accepted both children and loved them equally. In between, our relationship begun to experience several challenges — communication failed and we fought often. I always bent over backwards to make things work. Early this year, she sent me a message telling me that she decided to get married to another man who is HIV positive. I think she has been positive all this time and she could have infected me. Is it normal to marry a HIV positive person if one is negative? I am confused and fear going for testing as it could turn out positive. What happens to my son if she marries this man? {Concerned}