Memory problem?

I want to continue my work, but I do not save the new changes, I can not move, or create new pages, not save anything …
I think I read out there – I’m not sure about this – that as wordpress saves all previous changes, there comes a point that the memory capacity is over ..
If this is so, please tell me as I remove all previous. For example, one of my pages and is finished at the end has saved 300 above changes, I no longer care to have all these above changes, I only interested in my last saved version, I mean my final version. So if this is the case of memory problem, please tell me how I delete all previous versions to free up memory?

Thank you very much, I await your prompt response.