I am little confused by your question. The
depo provera shot is given once every three months not
for three months at some unspecified interval. If you mean that you received the depo shot 4 months ago, and hence, the last month, you did not get a repeat depo shot, then the answer to your question is, yes, you can get pregnant.
I was on the depo shot for about 5 years before stopping to try to conceive. It took me 3 years to conceive my son who is 6 years old.