My progress is gone

I created two worlds. One of them was in 1.11.4 and the last one was in 1.12.0. I had issues with both of them. The progress of two/three real life days wasn't saved in both worlds and I lost a lot of progress. I think it happened because I didn´t enter those worlds for more than one week. When I entered, both worlds were like I left them two/ days before the last save.