Trying To Get Pregnant, Off Birth Control For 5 Months

Trying to get pregnant, off birth control for 5 months now. Did an ovulation kit last month. Period was 6 days late when I am hardly ever late. Very light cycle, lasted 2 days. Feeling a hardness throughout my lower abdomen, mostly right in the middle. Negative pregnancy test. What could be going on? I feel like something is not right with my abdomen, uterus area.