My wife is currently four days late and tested positive for pregnancy yesterday. Today she started spotting and said "I think I'm going to have my period". So far she hasn't and we're waiting to see what will happen.

This same scenario happened a few months ago. Same situation except she took the test on either the day she was expecting her period or the day after. She tested positive. That was on Monday. On Friday she took the test again just for the hell of it and she tested negative. Then she had her period the next day. My understanding at the time was that she may have been temporarily pregnant, but that it quickly failed due to any number of possible reasons. We assumed it was a fluke. We conceived our first child the first month we tried.

At the moment, I assume its a 50/50 situation (we don't have any tests handy). I understand there is implantation bleeding, so it could be that. Or perhaps she's going to ultimately have her period and we'll know in a day or so. If that happens she is going to see the doctor about it.

My question is about the two week window around the expected period date (one week before and one week after). If she was pregnant, how long may she have been pregnant? Since ovulation? If she is now not pregnant (as was the case previously) what happened? If the pregnancy falters that quickly what is the probable cause? Lastly, if this pregnancy also falters, what could be causing this to occur repeatedly?

About my wife: she hasn't had caffeine in months, no medications, relatively healthy diet, 20-30 lbs overweight, 34 years old, not exposed to toxic chemicals, not under stress at this time.

About me: 35 years old, 20-30 lbs overweight, average diet, wellbutrin & lexapro for depression, protonix for reflux

Thanks in advance for any info. I know I'm asking a lot of questions for my first post.