I Been Trying To Convince, And Following My Basel Temperature.

I been trying to convince, and following my Basel temperature. I had a late period then started bleeding for 3 days. I had little to no cramps. Shortly after I check my Basel temperature. It was at 97.03 then next i had sex. But After that I had brown/black blood for a day Now I feeling a discomfort. Like cramping but not really that. Now I getting randomly sick but not like I'm throw up. Atleat not yet. I don't know if it nothing or something I should be check.