when did i conceive? whose baby?

I have on average a 30 day cycle. My last period was 2 August. My husband has left the family... he had an affair. But from time to time, he comes back to visit and we still have sex. This month, we did it twice... between 12-20 August (can't remember the exact days). However, I also had unprotected sex with another person on day 3 of my period.

I am 3 days late now. I have tested negative on HPT. I did the HPT about 2 dys ago, on the 1st day of my missed period.

In the event that I test positive, and am indeed pregnant... whose baby is it? I am hoping that it will be my husband's. But is there a possibility it will be the other guy's? What are the chances? Did I test too early?

I love kids... and if I am pregnant, I will keep the baby. But I need to know. Is there any way I can find out? I am worried sick, and anxious... and going crazy. My husband and I are Chinese, and the other person is dark skin. I've told my husband what happened, and he's not worried at all. But what happens if the baby comes out dark skin? Please, help!