4weeks since i had sex and still getting symptoms!

i've been on depo for a year and three months now, but i'm just now getting what seem to be pregnancy syptoms. i had unprotected sex two weeks(4-20) before i was supposed to get my next shot and 5 days late i was spotting, throwing up, and had bad cramps. i got my shot (5-2) and was not showing up as pregenant on the test. i was getting neaous and more symptoms of pregnancy.i took another pregnancy test on 5-13 and it came out negative. it has been four weeks since i had sex and im still getting symptoms. Could depo be cause the symptoms? Am i pregnant? when should i take another test? Could depo hurt the baby?