Actually, it's pretty common to have spotting or what seems like AF during pregnancy. With my daughter, I had brown spotting for 3 months every 30 days when my period was due. We found out when I was 6 weeks pregnant, but I had NO clue, because like you, I thought I had just had a period when in fact I was pregnant. I thought it was odd b/c it was the easiest period ever! No cramping or anything, and it was brown the whole time. Spotting doesn't always mean a miscarriage, I'm proof! Congrats on your pregnancy! :)
It is NOT possible to get a "period" if you are pregnant because women do not ovulate if they are indeed pregnant. AF ("period") is the sloughing of your lining in the event the egg produced that month is not fertilized. If there is vaginal bleeding during pregnancy depending on the amount it is normally called spotting. It can in no way be a period or AF. Normally it means miscarriage, but this is not always the case. What may have happened with you is you probably had a very early miscarriage and the HPT is detecting the left over HCG. Or you had a late implanter and a threatened miscarriage. There are a myriad of possibilities why you experienced the vaginal bleeding that turned into a brown discharge but only a Doctor can tell you what is going on with your body instead of us making speculations. Good luck either way:)
Wow! Congrats! Sometimes women will get their period even when they're pregnant, so it's not a surprise that this happened. What brand of test did you use? Just a word of warning, CVS brand tests give a LOT of false positives. A woman here even had her husband pee on one and it came back positive! I would say if you used pretty much any pink or purple dye test then it's accurate. You are so lucky to have conceived in just 2 short months. The majority of the women here have been trying any where anywhere from a year up to 10 years! I've been trying for 3 years.
Good Luck!