No, don´t worry.
Sheds are over stimated. You could have an increase in shedding rate, but you´re not going to go bald overnight.
Even this increase is not probable. Maybe it won´t happen anything. That was my personal case, and it´s also the answer doctors give when asked "the shedding question".
If you shed more after starting finasteride, remember that this shed is for good. You are going to get rid of short-cycled hairs to start producing healthier ones.
There´s also the finasteride induced Telogen Effluvium, that it´s said it can provoke lots of loss. It´s kind of rare, and you´ll notice you have it if you lose insane amounts of hair from even "safe" areas such as back and sides. If you suffer from this, hair will return to normal after stopping finasteride. But this doesn´t happen frecuently.
As I said, the highest possibility is to not notice anything, but the benefits (if so) from the drug.
