Did you recently restart your miner or did it run uninterrupted for quite some time?

Is this happening right now?

Investigating ...

Could you provide me with your wallet address? If you're reluctant to share it here please send it to info@poolmining.org.

There were multiple problems with your command line. 

1. Don't add http:// to the stratum address
2. Don't append the password like you did with :x

Correct way:

ethminer -SP 2 -U -S eth.poolmining.org:3073 -O WALLET_ADDRESS.WORKER_NAME --farm-recheck 500 --cuda-streams 26 --cuda-parallel-hash 4

Hope that helps :-)

Investigating. Are you using the one from here: https://github.com/ethereum-mining/ethminer/releases

And just to be sure, you did replace WALLET_ADDRESS.WORKER_NAME with your actual wallet and worker name did you?

Ah, I thought you mean the share counter at the pool website.

It mines Ethereum and only Ethereum.

The share counter does NOT reset of course. Any pool that did that would be an outright scam.

Pool host: eth.poolmining.org
Pool port: 3073
Pool user: 0xcb55abBfe361B12323eb952110cE33d5F28BeeE1
Pool pass: x
Algorithm: DaggerHashimoto

Resolving pool host eth.poolmining.org... OK
Establishing connection with proxy... OK
Establishing connection with pool 88.99.5.24:3073... OK
Sending mining.subscribe... OK
Sending mining.authorize... OK
Received mining.notify subscription... OK
Received authorization result... OK
Received mining.set_difficulty... OK: difficulty=1.5
Received mining.notify work... OK

Pool verification process is complete. Tested pool is compatible!

Yes. With PPLNS your shares are eligible for multiple payouts.