1st and 2nd day of period normal flow. 3rd day it was gone & came back in afternoon until now but light flow only. is there a chance of pregnancy?

Pregnancy not likely: But if really worried, can do a pregnancy test next week. A urine pregnancy test done correctly gives a reliable result 3 weeks after sex (3 weeks after when conception might have happened) or 1 week after getting a "weird" period or missing a period. If done sooner, a positive result is likely real, but a negative result may be due to testing too soon, and therefore lead to a repeat test.