Propecia and Male Pattern Baldness Question?

After recently discovering that I had Male Pattern Baldness, I decided to take the initiative and do something about it. After researching many medications an alternative methods to hair growth, I came across Propecia. After obtaining a prescription to propecia, I began taking it immediately in order to slow the process of MPB. After being on it for about 2 weeks I have noticed a significant increase in shedding. Is this normal and if so how long does the shedding phase normally last? Thanks in Advance.