a question, I have 4 x s5, yet I could find a block of this pool?

Anyone could find a block... and your chances are proportional to your hashrate, which means in your case the chances are very slim, but someone found a block with less than 1/4 of your hashrate.
For example (copied from nicehash)
5 TH for 24 hours = 00.18% chance of hitting a block
1000th for 24 hours = 36.49 % chance of hitting a block ...
but of course you may turn on your s5's and hit a block straight away

.. once even with a lowly block erupter i turned a bunch of them on and hit a 20 billion share in a few minutes... was shocked ..