My baby was planned and we do get this question all the time. I kind of assumed it was because we didn't tell them we were trying and because I am known to be a bit of a career person. It wasn't until I read this post that I realised how rude this question really is. I think most of the time people ask questions without considering if it was rude or not. I am sure they still care a lot about you. If you seem upset or emotional about the question, they may be picking up these vibes and misunderstanding them. If you act as happy as you say you are, I am sure they will feel happy for you too.
Good luck!