Got the depo shot on 3rd day of my period last month. now Im 3 days late. Light spotting Am I prego?

The depo shot will definitely affect your cycle, so being late isn't a huge deal. It will usually cause you to go completely off of your "usual" cycle, and can cause spotting instead of actual periods, and at different times in the month than you're used to. It can also cause you to eventually stop getting periods altogether.

Your doctor should have gone over what to expect with you before giving you the injection. They should have told you that it will affect your cycle, and that it could cause intermittent spotting at random times during the first few months, and/or cause your period to come early or late. You should call your doctor and ask them more about the Depo shot if you have more questions.

If you're still worried you might be pregnant, take a pregnancy test. If you are pregnant and are missing your period because of it, it should show up on a pregnancy test.