I've been using minoxidil for a year to prevent hair loss.however my hair started falling like crazy now! no new hair grew,so should i stop using it?

Minoxidil: Helps prevent further male pattern hair loss and may show modest effect on haiir regrowth. If rapid hair loss on Minoxidil suggest seeing a doctor or Dermatologist to rule out medical or mental cause of hair loss

Rapid hair loss: Something is going on beside male pattern baldness -- I suspect you have telogen effluvium (which tends to be self-limited) or alopecia areata (you'll end up completely smooth -- I have two friends, one a physician, who are like this; they're both fitness buffs, look great, and love it). A trip to a dermatologist is in order.