A causative construction is used, for instance, when we have / make / ... someone do something for us. For example,
"I had the painter paint my house".
We could render this passively too:
"I had my house painted",
meaning that I arranged for a painter to come and paint my house. Or another example:
"I had my car fixed",
meaning that I did not fix my own car rather I asked someone to fix it for me.
But sometimes, we use the exact same construction, that is, "have/get + object + past participle", to denote that we have performed something:
"I got my homework done" or
"I need to get this done by tomorrow".
I am confused! How can one determine when the construction is causative and when it is not?