Don't worry about it, easier said than done!!!! They are jealous and it does seem easy to them compared to the lot they have been dealt.
I have people saying to me all the time how easy I make having 4 kids and 1 on the way look, like you say its jsut how we go about it, but at the same time I see other people who I admire and I want to tell them, I kind of see it as a compliment??? I stuggle in the labour birth dept, long labours, back pain, ending in CS except 1 baby, so anyone who has a quick birth makes it look easy to me!!! See what I mean, it really is how we percieve things I say take it as a compliment, it will make you feel better, them being jealous or having false ideas on what it is really like walking in someone else shoes, is their issue.