Had withdrawal bleed after mirena removal, and took pt that was negative (1week since removal, 16 days since last intercourse)mean i'm not pregnant ?

Pregnancy unlikely: A urine pregnancy test gives a reliable result 3 weeks after sex (3 weeks after when conception might have occurred), or 1 week after missing a period. If done sooner, a positive result is likely real, but a negative result may be due to testing too soon, and thus lead to a repeat test. Negative at 16 days after sex is probably a true negative, but can retest if one's next period is missed.