[Jocelyn.]

I've heard of the shot giving people every crazy side effect you can think of... I've had nausea and spotting (basically no real period since I first got it), plus many many many others. Basically you can't really go off symptoms to tell whether you're pregnant. But since you didn't wait the full week for it to take effect (my doctor even told me to wait a month) there is a chance you could be pregnant. That's another downside of the shot, no regular periods to tell whether or not you're pregnant... so the only advice to give, like myss said, is to either try another home test because three weeks may have been too early or to go to the doctor and get a blood test.