Hello dear
Understand your concern
As pre-ejaculatory fluid contain sperm there may be chance of
pregnancy as sperm has mobility (less chance compare to penetration sexual intercourse). If sex during ovulation time has more chance but it not clear from your history.
As you had already period on 4th October, does not suggest pregnancy because most common feature of pregnancy is missed period.
Following are the feature of
implantation bleeding: more darker than normal period, just spotting that sink on pad or inner wear, appear 6-10 days after fertilization, more cramp than normal period but if cramping is gradually increased as day goes is not feature of implantation bleeding.
Implantation bleeding also accompanied with pregnancy symptoms like
nausea, sore breast, enlarged nipple, darker
areola and nipple, darkening of vulva,
fatigue, mood swings etc.
Now you can decide differentiate between normal period and implantation bleeding. If it is implantation bleeding, you can go for home pregnancy test in morning with fresh urine sample 8-10 days after missed period.
Hope this may help you
Best regards
Dr. Sagar