Hello,
If you had your periods after sex then it is unlikely that you are pregnant. Once pregnancy occurs, cessation of menses occurs.
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your doctor. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.
If you were bleeding for that long after sex I would have just assumed it was your period starting! Sperm can live in you for around 2-5 days (sometimes longer in healthy conditions) but if you were bleeding in that time then most of it would have been washed away by the bleeding. I'm not sure, that;s weird. Are you sure you weren't already pregnant when you had intercourse and that;s why you were bleeding? Sometimes in pregnancy you can bleed after sex.