I am 18years old, I got my first depo shot in April and went for my second one yesterday and the nurse said I was a month late, I still haven't had a period, I have pregnancy symptoms but I took 1 pregnancy test and it was negative can I be pregnant as I have had unprotective sex for a month.

It is still possible for you to be pregnant. Anytime you have unprotected sex (even if you are using multiple contraceptives) you can become pregnant.

Also, pregnancy tests can give false positives as well as false negatives. You will want to take another pregnancy test to be certain.