Mine showed an exteremely high level thus they are suspecting Premature ovarian failure. Me cycle is usually by the way 30-33 days. I have a 4 year old daughter

Did your doctor give an indication as to why they did the test on day 20?

FSH is usually done around day 3 as this would basically give an idea of how hard your body is working to try and stimulate egg maturity prior to ovulation. At day 20, you would have likely already ovulated. Sometimes the test will be done again a bit after day 3 if Clomid is used to determine the effect, but not at day 20.

I would contact your doctor and ask more questions. If this was the only time the test was done, I would also ask for it to be repeated. May I ask what your FSH level was?