Welcome to HCM.
There are always chances of pregnancy after unprotected sex.
You have to careful for that.
Confirm your pregnancy by urine pregnancy test or USG.
You can take mtp pill if it is positive but you have to stop breast feeding for that period.
Consult your gynecologist for better guidance and medical management.

Hello and welcome to HCM.

Thank you for your query.

I have gone through your query, and although 2 weeks since your last period are quite sufficient to result in an implantation bleed, a pregnancy cannot be ruled out.

The only other possibility is an infection, for which you should have other symptoms like:
-Burning sensation while urinating
-Frequent urination
-Increased urge to urinate, but less amount of urine passed
-Chills
-Fever
-Lower abdominal and/or flank region pain
-Itching around the genitals
-Blood in urine or immediately after (not always seen)
-Vaginal discharge
-Painful intercourse

Although not all would be present. I would suggest the following:
-Go about a urine analysis, to check for the presence of an infection, if confirmed, the infection could easily be the cause for the bleed
-Pregnancy should and will have to be ruled out, as you have not provided information on when your last sexual contact was, it would be best to conduct a home pregnancy test at least 2 weeks after the sexual contact or on or after the first day of a missed period. An early morning urine sample would yield a most accurate result. You might have to repeat this 2-3 times to confirm a result.

In the meantime, please abstain from all forms of sexual contact and drink plenty of water.

I hope I have succeeded in providing the information you were looking for. Please feel free to write back to me for any further clarifications at: http://doctor.healthcaremagic.com/doctors/dr-shoaib-khan/64581 . I would gladly help you.

Best wishes.