If you are having these side affects after one shot, I would strongly suggest that you find an alternative birth control. What you are experiencing is common side effects with depo. Search the web for info on depo--it is very scary. The fda has issued a "black box" warning on the side effects, which includes loss of bone density which is likely permanent.
As far as conception after depo, again search the web. The research shows that it takes 6 months to 2 years for women to conceive after stopping depo. The actual statistics are:
50% of women can conceive within 10 months
two thirds of women can conceive within 12 months
83% within 15 months
93% within 18 months
hope this helps! There is alot of literature now available on depo. I sure wish someone had warned me!