It can be either a 'local' account on your machine, or a microsoft cloud account... You probably have both types set up, hence the confusion, but have been changing only the local account password each time.
When you keep getting the password reset text message I assume this is to reset the cloud account, as microsoft shouldn't have any knowledge of the local account (which is stored only on your PC).
You need to take control of both accounts and standardise on using only one of them every time. When it asks you for the password does it state somewhere which account it wants you to log in to?