If I understand you correctly, you bd'd three weeks and four days ago and you are wondering if a HPT would show positive after that amount of time and I believe that it would. Most HPT's will register positive on the first day you miss your period and many will register positive even before you miss your period. It generally takes nine days for the fertilized egg to implant into your uterus. I would think the HPT is correct, especially since you had a flow even if it was somewhat abnormal.

How long does it take the egg/sperm after it has been fertilized to implant? I think my husband and I bd during a time I could have been very fertile. We bd twice during that time. The first time would make 3 weeks and 4 days ago today, and the 2nd time would make 3 weeks even today. I'm not sure exactly when the first day of my last period was but I have a pretty good idea-I know the week I had it , just not an exact date and according to a chart I have I could have been very fertile during the time we bd. A few days after we had bd I cramped on and off for about 2 weeks(do not cramp like that before af and do not cramp that far ahead of time) It reminded me of the cramping I got when I was pregnant with my son(at that time I thought I was about to start af and I really was preg.) Anyways 7 days ago I started my period(I don't know if that's what it was though) I believe that day would have been the day or close to the day I would start my period anyways. I bled for 2 days and then it stopped for a whole day and then came back , but very very light almost like spotting for about 4 days and then it was like brownish spotting. but the first 2 days it was like a normal flow period-red, and kind of heavy. I have had my period for almost 20 years and I have never had an irregular period like this before. I usually have a regular flow period for a whole week that does not stop like it did. Is there a chance I could be pregnant? I've taken a few hpt and all are negative , the last one I took was last night. Could it still be to early to show up? I'm thinking about going to the dr. to test to see. How much longer should I wait before I go? Could it be that it took a while for implantation to complete and hormones are just to low? I'm really anxious and excited to find out.