Hi there,
I have read and understood your questions and will try to answer all of them to the best of my ability.
1) Having unprotected sexual intercourse one day before periods does not usually lead to
pregnancy.
2) However, there are instances of delayed ovulation where you ovulate late and so can get pregnant towards the supposed end of a cycle.
3) Since you have not got your periods and are having
unprotected intercourse, there are chances of pregnancy.
4) Spotting, fuller breasts and backache might mean pregnancy, but are not very reliable indicators of the same.
5) Hormonal imbalance is also a possibility.
6) My suggestion is that you do a urine pregnancy test almost 3 weeks after an unprotected sexual intercourse. If you want earlier result, you can go for a
blood test called
serum beta HCG.
7) In case both are negative, you might not be pregnant and might be having minor hormonal imbalance for which you might need to take
progesterone pills for withdrawal bleeding.
I hope this was helpful.
Regards,
Dr. Shikha Shah