you really really really should ask your Dr. about all of this - no-one on here is going to be qualified enough to give you a reliable (and safe) answer.
Good luck :-)
No wonder you got a negative - it was only 4 days ago! Home pregnancy tests measure the level of HcG, a hormone released when you're pregnant and the levels of HcG are never high enough u. ntil around the time you expect your period. So you wouldn't have got anything but a negative by testing...