I knew that feet get bigger in pg, but didn't know until several months after dd was born that mine weren't going to go back to their old size! I can wear most of my old shoes, though, but some are out of the question.
I think it's not at all uncommon. The extra weight you are carrying plus the relaxin (when it comes) cause the ligaments in your feet to stretch. The bones spread out and the feet get bigger. Ligaments do not bounce back like tendons to, or if they do, it's very slow.
I would suggest, as you are choosing new shoes, to look for quality ones with good support. That will minimize the effect.