It sounds like the game was not properly saved when you exited. So, your character got saved, but not the world. When you exit valheim, make sure you do it properly using the exit button on the menu. Do not force valheim to close or use ALT+F4.

Also, consider manually saving the game before you quit by pressing save from the menu. If Valheim does not close properly, there will be problems like you describe.

It is important to understand that valheim actually makes 2 saves. There is the character save and the world save.

The problems you describe are related to world saves, not character saves. You may have created a second world without realizing it - double check to make sure you are on the correct world.

It is also possible to create these problems by toggling "Cloud Save" settings. If you change your cloud save settings you risk accidentally overwriting the world with a new world. Make sure you do not change your cloud save settings unless you know what you are doing.