I took medroxyprogesterone in Jan. to start my cycle I had a normal cycle in Feb.8-13 but in march my cycle lasted for 2 days only and it was very,very light march.13-14 then it stopped and I haven't seen it since it is now may.5 and still nothing could I be pregnant.

The best way to know if you are pregnant is to take a test or go to see a Doctor. It is possible to get pregnant while taking medroxyprogesterone. If you really think you are pregnant you need to stop taking it. It has serious side affects on an unborn child especially in the first few months. Here is a link to a site that can really inform you about medroxyprogesterone. Good luck!
Medroxyprogesterone Information from Drugs.com

While it is possible, it is rather unlikely as amenorrhea (no periods) seems to be one of the side effects of this medication.