Why cant my parents be happy for me?

I am pregnant with my 3rd child (about 6 weeks) and my mother knows, she wont stop saying things like 'it isnt really even viable til 12 weeks anyway' and 'oh well I suppose next year you are just going to have to try your best to keep your head above the mess. Its such a shame, 3 more years and Ryan (my son) would have been in full time school and you would have been free' . My dad has been saying for years for me not to have any more children and that 2 is enough, I am one of 2 and nobody in my extended family has had more than 2 kids before. This pregnancy was a shock for myself and my husband too. I have been working for the past 6 months after having 5 years as a SAHM and it is only a 2 day a week position, but it has made me realise that there is no way in hell I am doing 5 days a week until my children have grown up and left home anyway. My daughter will be 6 and my son will be 3 when this baby is born, my husband earns very good money and we are doing just fine, why can't my parents just be happy for me? Why cant they just say congratulations and not ask questions, just be happy!!??