I dont have an answer for you here, but I've recently started Prozac (Fluoxetine) and my cycle's been a little hard to follow. Maybe just new stuff entering your system messes up the cycle a little?
No, a period and a negative HPT (used at the appropriate time) indicates no pregnancy.
No
The negative pregnancy test is the defining answer, regarding pregnancy - once your period is a week or so late - if you are pregnant, the hCG will be high enough to be detected.
Most likely your period. You're probs not pregnant.
. . . means that you arent pregnant.
Yes
No you can't be pregnant and still have your period. You can have a light bleed but not a period. As for the whole negative test thing, it could be a false negative.
Unlikely - the bleeding probably was your period
Having your period means you aren't pregnant
You are pregnant
Pregnancy tests are not 100% accurate, but being that it was negative and you got your period, I'd say you are definitely not pregnant.
Most pregnancy tests are 99%