Using minoxidil but if I am washing my hair, there is lot of hairfall.

All humans experience more hair loss on a shampooing day than a non shampooing day. It's the water and scrubbing that facilitate the hairs to come out not the shampoo. Similarly, increased shedding is normal in the first 6-8 weeks of starting minoxidil (Rogaine). See your physician if high levels of shedding persist.

Minoxidil can initial cause a shed for the first two months, but after than it should not cause hair loss but hair improvement