Hello and welcome to HCM,
I would like to give you some information before I answer your queries.
Pregnancy test becomes positive 10-14 days after unprotected sex.
Thus, urine pregnancy test should be carried out 10-14 days after unprotected sex.
Implantation occurs around 6th day after unprotected sex.
Implantation may be accompanied by light pink discharge, lower
abdominal pain,
bloating sensation, increased appetite etc.
A negative pregnancy rules out pregnancy for practical purposes.
The spotting that you are experiencing could be due to onset of
menstruation or it could be spotting that accompanies ovulation.
You can wait for the onset of periods.
Little variation in cycles is not of any consequence.
Thanks and take care
Dr Shailja Puri