"Given the most ideal conditions (ideal vaginal/uterine environments, fertile CM, strong sperm health, etc) sperm may be able to survive between six and seven days," according to http://www.early-pregnancy-tests.com/sperm.html. So whether or not you could have conceived depends on a lot of factors, like sperm life span, fallopian tube environment, when you ovulate, etc.
Call your doctor's office to discuss whether the symptoms you described could be related to the shot. This is something you should have discussed with your doctor before you got the shot. If you want good reproductive care from your physician, you've got to be open about what you're doing in your life. If you don't feel safe talking to your doctor, there's a problem: either get over your shyness, or find a doctor you can trust. This is a very important issue.
NEVER have unprotected sex unless you are willing and ready to accept the burdens and responsibilities that come with that action (pregnancy, std, infection, etc.).
