truck wont start, and i dont think its the starter

i say that becuase i replace the starter every time and its always the same thing. sometimes it will start and sometimes it wont. i could go start it up, drive to walmart, park it, go inside, come out, and it wont start. what do you guys think?

Have you had the battery & alternator tested yet??

yeah battery was a yellow top altima and the alternator was replaced a while back. both are good.

Ignition switch, starter solenoid, starter relay did you check those?

Try the Battery cable ends as well as the cables that connect to the starter .... had that happen to me a few times.

IS IT TURNING OVER AT ALL

check battery terminals and the cables going to your main ground and starter and solenoid if applicable. I have personally troubleshot similar problems, twice on Honda's and one time on a toyota celica. and what I found was although the factory thick gauged wire looked fine on the outside jacket, the wire inside was burnt and or corroded to the point where current could not flow.
It is possible to have voltage if you have checked with a meter and still have little to 0 current. you will need a clamp-on ammetter to check this(like an electrician uses not a digital volt or multi meter)

just because its a optima doesnt meant it doesnt go bad. i have been through 3...

clutch cancel switch

you mean neutral safety switch? depending on the car and if its manual, that could be something to look at but i would look at the relay first and foremost. and all your grounds.