It could be that you bought pvc that was too thin (diameter-wise). 1/2" is very bendy. If you go up in thickness by one or two sizes( 3/4" or 1" pipe), it will be stronger.
What are you using to join the pieces together ? Perhaps you could find a short piece of thick dowel that fits snuggly inside the pipe, and use that to strengthen the connections.
Do you have any handy friends, relatives or neighbours that you could ask for help?
We have used PVC pipe in the past, but have switched over to 1/2" metal conduit steel galvanized pipe because it is strong and does not "droop". It is thin enough that you can cut it by hand with a hacksaw. The pipe connections include screws.