Just to add my words of encouragement to the others...
My thread is the last in jerry a. laska's list of links above.
I have an upcoming trip LHR-LAS LAX-LHR flying out in F
I booked it with a 2-4-1 last May for this May and bagged 2 in F. Currently in J on way back but have Expertflyer alert set up to check for F seats
Just keep trying - seats do often get released and for F this is often sporadic
^