Could i be pregnant and test be negitive?

Ok I'm diabetic and have irregular periods mostvmy life then it got back on track every month for six months. I haven't gotten it this month or last month I've taken pregnancy test and they come up negitive I've been having really bd cramps non stop for almost two weeks now I'm tired a lot too. I was wondering if me being diabetic may cause me to not produce enougj hormones for a test