Freaking out!

Okay guys, i went on birth control for the first time on april 5th. My dr informed me that the shot starts being effective a week after you get it. My bf and i had sex before that first week, we used a condom. Now the last 3 days Ive felt nauseous, thats the only symptom I’ve had. So idk what’s going on. Could i possibly be pregnant or is it just the side effects of the shot? Its hard to tell since the side effects of the shot are quite similar to when you’re pregnant. (Please don’t say just take a test)