Why am i so nauseated?!?!?!?

went to the Doc a couple days ago bc of chest aches...no cough. thought i had pneumonia, but xrays came back normal. They put me on prednisone which is a steroid to help the infection in my lungs and a z-pack (5 days worth of azythromiazyn antibiotics) my chest is better but i am SO nauseous! I just had my period like 10 days ago (it started 10 days ago) so i know im not preggo but its just like the constant nausea that i had with both of my pregnancies! could the steroid be causing this? i know the antibiotic could make me queasy but the last time i took it was last night around 6:30 so i dont think id still be feeling the effects. ive been drinking tons of water! i dont get it! what could it be?!