I say go with your gut chickie. Having 2 close together is hard, and stressful sometimes - and I got an easy baby the second time round!! But its getting easier (I agree with Ali about the after 6 months it gets easier) and I love to see the kids interact - its so cute how DS does a silly dance just to make DD laugh.

At first I regretted having them so close together - DS has sleeping issues too, but they are getting better now that we have dropped the day nap - but now - its getting really fun!!

Starting to think about when I'll go for number 3 - could be sooner rather than later
Good luck with what ever you decide. Do what you think is best, don't let people pressure you into having a baby that THEY won't be helping to take care of.

You'll be fine no matter what I think