Pocketbook Touch HD froze/stuck on book page

Hi guys!

I hope anyone can help me out. I've got a Pocketbook Touch HD.
Never used it a lot so finally was using it a bit more lately. While I was reading an ebook, I wanted to go back a few pages so I clicked the button to go a page back a few times. Then it got STUCK. It's now on one book page, still showing as if it just went back.

The ereader doesn't react to anything anymore. The LED light still works, just as the green light from the power button. It seems to still turn off and on as the LED background light goes on when the power button is on, however, the page stays the same when turned on or off. When I click any button, the green light flashes shortly.

So far I've tried:
- Connecting to a computer or charger and holding the power button for 15 seconds (probably held it much longer too). Tried it without being connected to the charger as well.
- Holding the backwards and forwards button at the same time.
- Holding the home button and power button at the same time.
- Holding the backwards and forwards button and the power button. I probably held every button combination possible.
- Using a paperclip to press what I found was the reset button (the small hole next to the power button)
- Charging it a full day and night. Didn't help.

The computer doesn't see the device anymore either when I plug it in.

I'm very desperate by now. Is there anything I could still possibly do? Would maybe inserting a SD card with anything on it help? I also read about letting it run out of battery completely, however since I used it not that much the battery is still really strong and could take a loooong time to drain.

Hope anyone could possibly help me!