I have heard that minoxin causes faster shedding as it works. Is that true?

Follow up with your doctor.  Topical minoxidil is for treating hair loss.  It does not cause hair loss.  Some have reported initial shedding in the first month.

Yes, minoxidil can cause some additional hair shedding when started. This is probably a good thing as it indicates the hairs are being influenced by the drug. They should regrow, possibly after a dormant period, and then hopefully be more stable. Remember it can take 6-12 months to see the benefit from use of minixoxidil.

Yes, minoxidil causes shedding in the first 4-8 weeks of use. In fact, any treatment for genetic hair loss can cause increased shedding (including finasteride and laser) but minoxidil is particularly well known to have this effect.