Time travel and parallel universes

I have a theory that hopefully I will elaborate on at a later time. Now, I have no proof for my belief. Then again, there are established beliefs that are not proven as well.

I believe that our existence in time is all occuring concurrently. Things are happening now no matter when it happened. Also, things happen that are meant to happen and cannot be changed. Our futures are static because they have already happened or about to take place as they are meant to. The time paradox of someone going back in time to change their present or future will not occur. If someone were to go back in time, it would have already happened and was meant to happen so it does not change any events from that point forward.

Since our future is already planned out, so to speak, this eliminates the possiblility of parallel universes where each moment in time can be splintered into thousands of alternate realities based upon our actions.