4 spokes in one ride means that your spoke tensions were not happy. While your wheel may have looked nice and true, it's always possible you had some over-tightened ones and some wobbly loose ones. Good spoke tension and wheel trueness do not necessarily go hand in hand, and it's quite common for someone who is just learning how to build wheels to focus on the latter at the expense of the former.
The easy way to check is to just manually squeeze every adjacent pair of parallel spokes to see if each pair feels about the same, all the way around. Do both sides. Then do a pair on the left vs a pair on the right, all the way around. They should all give just a little.
I'd recommend you go back to your co-op and explain you busted 4 spokes in one ride. They'll know what to do. They'll be able to tell you whether one side of your wheel is too loose, straining the opposite spokes, or whether your whole wheel is too tight, straining all of them. Most co-ops have a bucket of old spokes you can have for near free if you can find the right size, a much better deal than paying $3 each or whatever ridiculous price your LBS will charge you.
My last piece of advice is to check your tire pressure more often and quit charging curbs and potholes. Wheels last longer when you are nice to them.
