Just a little rant

Katie
Okay, so I work in a bank in the U.K., and today a customer asked me "when was I due?".
Being in my fourth year of infertility I feel like this has killed me a little bit inside and I don't know what to feel? 
I normally wear baggy uniform but today was washing day so I had to wear an old cardigan. 
Does anyone have any tips on how to deal with these kind of questions?
She was about to ask me whether I wanted children but I made a comment about being lactose intolerant, which I am, to diffuse the situation. 
Any thoughts or feedback would be greatly appreciated.