Sexually active on 9/17/22, in september n middle of october had ultrasounds,urine and blood tests done all negative.took another pregnancy test within time limit was negative, checked hours after, thick faint pink line hours later. what is this?

Negative urine and blood tests with ultrasound in mid October rule out conception with sexual encounter on 9/17 so I am not sure why you decided to do the urine tests again.

If it was the same stick that you checked hours later, that would give a false positive signal. It is important to follow the instructions for the test carefully and read the stick within the prescribed time.