Practically, just wanted to send some non-MN hugs to you as well and let you know you're not alone.
I am, in a lot of ways, in a similar situation BabyScout is 15 months and I know SO MANY PEOPLE who have babies of a similar age who are pregnant with number two. Sometimes I feel broody and think "aw, that probably won't ever be me again" but most of the time now I think "Thank goodness that's not me!" I feel for how harrassed and exhausted (physically and mentally) all of my friends/family that have more than one always seem, how much more expensive their lives seem, how hard it is to negotiate multiple small personalities in addition to your own and MrHusband's, etc. Having one means I can focus on just him teaching him, playing, ignoring letting him get on with what he wants to do. It takes me ages to get just he and I out of the house -- I can't imagine trying to load up/hustle out a herd of children (or even just a toddler and a baby). (My SiL has 5 1/2 and honestly, I don't think they're ever on time for anything, no matter how early they start the loading process and I've seen the loading process take nearly an hour a few times!)
But sometimes I think -- oh, I'd like to be pregnant again or give birth again (even though I didn't have "the dream scenario" I'd do it again) or breast feed again (see previous message on thread about giving up if confused) or I miss the looks people give a new mum and her baby (that sounds very egocentric written down but it aways seemed sweet to me the way the old dears/small children/other broody moms) would coo over a new BabyScout) or (and this seems to be the hardest for me to give up) I'll never get to hold a just born baby that I just gave birth to and is the splittin' image of MrScout.
As the days go by, and BabyScout gets further and further away from his newbie status, I love having just one. The freedom of only having one personality to deal with/focus on, of being able to do what I need/want to do without having to take into account differing nap/feed schedules and only having one crying baby/toddler/child, not a houseful.
I can honestly say if I had more than just BabyScout right now, given the meds, I would not be coping.
So in my long-winded way, PI, I wanted to let you know you're not alone and don't feel you need to struggle alone. Keep coming/hanging out here in the tea room. I've found these wonderfully fabulous ladies have helped me a lot with dealing with my ishoos of having an only (whether they realize it or not).