Try this:

1) stop stroping on the strop.
2) strop on newspaper over glass plate for 100 laps, see how it goes
3) if step 2 hadn't got you to a nice shave, try 100 more laps.

When you decide to try stroping on the strop again make sure the strop is level with the ground (it's a lot harder to strop right if the strop is not paralel to the ground).

just my US$0,02