Rear wheel keeps going out of true?

i built my wheels and they were spot on. the front is still fine but the rear is being a pain in the arse.
after truing it i get on for a ride and i can hear the spokes creaking. after 5 mins i check and the wheel is out of true..starting to drive me mad now.
any ideas on how to keep it straight?

detension and then retension properly.

will it not do the same again though?

Did you oil the threads ?

Did you oil the threads ?

yes...i thought that was the right thing to do?

am a newbie here how do I get a flat spot out of a rim that I have just built?

Yes it is the right thing to do. After building/truing & tensioning the wheel, squeeze every single spoke in pairs (i.e every pair of spokes that are near parallel need squeezing). The noise is coming from the spokes untwisting, if that makes sense

so i need to loosen all spokes and start again, as mentioned earlier?

what tension are you going up to?

are you stress reliving while building?

No, just squeeze all of them until they all ping, then retrue.
Repeat as necessary :)

repeat this process until up to tension (typically 100Kgf for road wheels w/ aluminum rims -- but check the manufacturers website for specs):

lateral true
radial true
dish
add quarter turn of tension
stress relieve (lay hub on block of wood with axle vertical and push down and around the rim on both sides -- get all the pops out)
measure tension of each spoke

repeat as necessary

i didn't realise there was so much to wheel building. i think i better loosen them and start again following the above advice.