Thanks for your question and concern According to you, you had a sexual intercourse on 1stNovember with that women and you also know that she is sleeping with another guy at the time and the date given by the doctor was 5th august and the child was born before the date on 28th July so the chances of baby being yours is very low because the date of conception must be 8th to 16th November and you got sexual on 1st November so chances is low. I would suggest you that you can take help or you can request your health care for a paternity test that will ensure your doubts. Do go for paternity test and be sure for it.Best wishes