Hi there, I have understood your concern. I will suggest you the best possible treatment options.
1 ) First of all do not panic.
2 ) As you might be aware that in a woman with regular cycles day 10 to 20 of the cycle is the most fertile period of cycle. If you have unprotected sex act in the fertile period of cycle, then you stand chance to get pregnant.
3 ) You are right in suspecting The
implantation bleeding, in the third week of the cycle.
4 ) In my opinion, it is too early to expect the symptoms of
pregnancy. I will suggest you to wait for your expected date of the cycle . If you happen to cross your dates, then you can get morning's first sample of urine tested for pregnancy.
In case of doubt blood
beta HCG test and USG will be of help.
Blood beta HCG values below 5 indicate no pregnancy and above 25 indicate positive pregnancy test.
I hope this answer helps you.
Thanks.
Dr. Purushottam Neurgaonkar.