We have reverted the Experience required for your levels, so everyone should have their levels back now (or higher depending if you gained xp since yesterday).
Again, no Experience was lost in any previous changes, we only did some alterations to how levels were calculated but they are now reverted back to their original levels.
We'd like to remind everyone that this is an Early Access game. We try different builds all the time in order to find what works the best. A Lot of things are being changed constantly - with some things being majorly changed. A lot of things get reverted after testing them if we see there are issues, or adjusted further, while some stay if we see it's working. It all depend on the feedback we get from our players. You find that a change was bad? Great! Just let us know about it and we will look at changing it if enough players agree with you.