What do you presume to be the source of whatever it is that determines changes in its state?
That doesn't even make sense - we are talking out how minds work and make choices. It's about
how come you wished to do what you did at the time you made your choice - as in your previous statement about how you could have done differently
if you'd so wished. We're talking about
why you didn't wish to do differently.
You keep on insisting that it's "you" that is making the choice and seem unable to grasp that "you" isn't a magic black box that we are forbidden from asking questions about. Your choices, your wishes, are what they are at a particular point in time
for reasons (unless they are random).
Because your state of mind (what you wish to do and think) is changing over time, it is either operating as a
deterministic system or not. There is no "source" other than your own mind (its ever changing state) and the external inputs.
In other words, your state of mind now is either entirely because of what it was just before now and its current perception of the world, or it isn't, in which case its current state is partly for no reason at all.
And no, having a non-physical soul with a "conscious will" makes not a jot of difference to that because its state and its will would be part (or all, if you like) of "you", that is, your state of mind.