Thanks for your query.
Since you had your regular period, I do not think there is a chance of pregnancy
The pain and cramping could by because of ovulation, however ovulation just three days after your periods is also rare.
You could be having mild gastroenteritis
or an infection that is causing such cramping.
is also incidental according to me.
Since it is too early to test for a pregnancy, the only way to know whats going on is to see a Gynecologist if the cramping is really worrisome