The best thing to do right is NOT stress - I know that sounds difficult but let me assure you that two babies in around 12 months is very 'do able'.
I fell 'unexpectably' pregnant with my second baby when my first was only 11wks old

I thought breastfeeding was a good contraception!! lol however although the first year of having two 'babies' on my hands was a VERY busy one ( they are 12months and 7days apart) I still managed and now am reaping the benefits because my girls are THAT close and they love each other so much - its almost like twins - they have been companions from day one.
The only way I managed was to get my babies into a sleeptime/feedtime/playtime routine. I could not afford my health(or my sanity for that matter) to be up all day and all night with 2 babies feeding all over the place. Sleep was THE most important thing to my exhausted body. Without structure I would have been lost.
Do you breastfeed or bottle? If you breastfeed you may find your milk will dwindle off or that the baby will lose his taste for your milk as it turns from 'sweet' to more 'savory' like when you are pregnant. If you are bottle feeding then of course you wont have any problems and it wont 'tax' your body so much trying to 'grow' a baby and 'feed' one too.
Try to stay positive and let anyone who tries to throw any kind of negativity at you be as water on a ducks back. People who made cracks me made me more determined than ever to prove them all wrong - which I did!! My children are settled and happy and a true pleasure to have so close together. It may be hard work in the beginning but the pay off in the end is HUGE
