More on time travel in PoA

[fun_n_games_2663]

No: HPFGUIDX 43559

I'm a new poster.  I'm sorry if this has been covered, but I haven't 
seen it.  When Harry first goes through the Shrieking Shack sequence 
(as we understand it to be the first sequence), and is about to be 
done in by the Dementors, he is saved by a patronous that we later 
find out he conjured.  When Harry goes through the time turner 
sequence, he realizes that he is supposed to conjur the patronous and 
does so.  Now, here is my problem--If Harry hadn't already gone back 
in time once before, wouldn't the Dementors have gotten him the first 
time?  If he hasn't already gone back in time, there won't be anyone 
to conjur the patronous.  I believe that we only read about two 
sequences in the book, but there must have been others which occurred 
before what we read.  If this is the case, then many possibilities 
open up, many of which I hate to mention--such as, was PoA in "real 
time" at all, or was it all a trip back in time?

"fun_n_games_2663"