Fell on my knees.right kneehad no fracture(x-ray).had fluid there.fluid was gone after a few days.after1month,hit knee again,got little fluid.problem?

Bursitis.: It sounds like you had two separate episodes of what we would call prepatellar bursitisThis happens when we fall on our bent knee, hitting our patella into the ground. It's inflammatory and usually self-limiting, as you saw after the first episode. Hopefully the second will behave similarly. If not, you might need an examination and some testing. Give it a couple of weeks.

I'm less worried...: ...about your knee than I am about why you keep falling. Has the latter issue been addressed please.