Hair return from discontinuation of Minoxidil shed if I stop just after 3 weeks?

I would advise seeing a physician to review. You shedding will likely improve ina few months, yes. But whether your density will return back to the way it was is not guaranteed.

Minoxidil helps to stopping hair loss and thickening of hair although it may cause a little loss at beginning . But ıf you stop to use minox after a long time usage, you may experience a fast thinning, even loss of hair because of ending action of active ingredient. That phenomena leads people to a misconception that minoxidil causes hair loss after  stopping to use it. hair will not return where it was before you started  and stopping

Minoxidil sheds occur when minoxidil dependent hair has grown. This does not happen in 3 weeks, it take much longer so you should be able to stop the medication now without worry