just want to say congratulations, and you can do it!
our first born was 11months old when we found out we were having no2, (original plan was start trying when he was one, thinking it would take forever!) the boys are 19months apart, budget wise, we couldnt afford it, we were living at his dads, me a stay at home mum, he was on job search, taking longer then we thought to get another job. i had no idea how i would manage, but some how i just did, you adapt to the change, and the new bub just kinda fitted in.
now in a simmilar situation again! my dd will be 13 months when bub4 is due, the boys are now 5 and 3.5 they have there ups and downs, but generaly get along. both dd and this bub are whopsies bubs, (both were concived while on the pill, it dosent work for every one!) dd wasnt planed untill next year some time, when ds1 started primary school, but these things happen for a reason.
i love all my babies, even if most are whopsies!!! i think its natural that you feel stressed about it all, after all a baby dose change everything, but if you managed with your first, then you will manage with 2, after all you already know how to deal with a newborn right? the best thing i discovered was, dont try fit your life arround the new bub, make the bub fit in arround you and your routine.
hope this helped!