No...It's called orgasm control (edging) and it can be good for you (differing opinion alert).
It can give you a sense of euphoria that you don't normally get. It also can help you last longer when with a partner.....because you are actually "learning" control.

As far as hair loss, no you would not have increased hair loss immediately after ANY activity...there simply is physiologically not enough time.

Also I think you may have misunderstood your doctor (masturbation=bad)....it's entirely possible that what he was saying (and this is just how I would take it so it's pure conjecture on my part) was that higher testosterone levels can result in baldness (it can)...and he was merely asking if you had a high libido.
Just something to consider.....

There is propecia (I believe rx required, someone correct me if I'm wrong) It may affect your libido.
And, as mentioned minoxidil (Rogaine)

Masturbation does not cause hair loss.

There is a libido/hair loss connection......but if it's preferable to you to have a lower libido, then that's a whole other debate that you have to have with yourself.....and it would involve messing with your hormones.

Speaking from a woman's perspective and my own personal opinion....bald is a good thing.

ETA.....NO GUILT....Repeat NO GUILT..... if it's all consensual either between you and you or you and another adult WHO IS ABLE TO GIVE CONSENT....