If I'd never met DH (or, y'know, anyone else)... honestly, I don't know what I would have done. I never really thought about it. I met DH when I was doing a Screen & Media and English BA, and I probably would have kept doing that (possibly even a little better, due to spending less time in the computer labs emailing DH!). I might have then gotten the same job I did, as a behavioral therapist, or I might have been more motivated to seek a "proper" fulltime job. But I'm not a very careery person. I might have done some postgrad study, but it wouldn't necessarily have done me much good.
If DH and the kids died in a car crash, though? Me as I am now? That's a different story, even if we leave out the grieving process and the decent chunk of life insurance I'd get. :p I can think of a ton of things I'd like to do.
Study midwifery, or something baby-related. Try to get a "proper" job as a writer for a pregnancy/parenting magazine (like the one I currently write for), or some other... writey... jobby.... thing. TRAVEL! I wouldn't mind taking a menial job to earn money to backpack around Europe, although with my sense of direction that might end badly. Volunteer (I lean towards something involving pregnant women). Try out for plays and Broadway shows, and take classes in singing, acting and dancing. Do more extreme sports... well, not sports. Experiences. I did skydiving recently - a long-cherished dream - and it was fun, but actually not as exciting as I'd hoped. I want to paraglide and hang-glide and stuff, but I can't justify spending DH's hard-earned money on it! I'd also like to take some interest papers at Uni, in random subjects like psychology and anthropology and fashion design.
That said, I went through a real phase of feeling trapped and unhappy a year or two back. I felt like I was just starting to discover myself, but was being thwarted by the existence of my high-needs baby, and even (through no fault of his own) my husband. I don't feel like that any more. Back then I was depressed, tied 24/7 to a difficult baby, freaked out by the prospect of another traumatic birth, and doomily convinced that I'd just have to bite the bullet and suffer through the next twenty-five years or so before my kids left the nest and I could try to scrape my worn-out, pregnancy-raddled self back into some semblance of a human being.
Somewhere along the line I changed my attitude - not in a dramatic movie-of-the-week way, and it was probably largely to do with getting a bit more sleep. But I decided to focus on all the stuff I could do, even with a baby. I started a singing group at my house, because I couldn't go out to choir practices. A few years later, we just finished practicing for a performance at our church carol service (which, don't get me wrong, is the least glamorous venue in which one could choose to perform... it's not like "next stop, Carnegie Hall", but we have fun and sound, um, OK). I started freelance writing, because I could NAK, and a few years on I regularly publish articles for one magazine, and occasionally for others. I started a blog, and a few years on... well, it's read by, like, ten people, but at least I'm writing.
It's all baby steps, from my current life to the life I imagine myself leading. After two years in this house I finally put up hooks to store the aprons neatly, and felt like Martha Stewart for the rest of the week. :p I don't own a self-sufficient homestead yet, or perhaps ever, but there are a heck of a lot of pots on my deck, growing yummy things.
And doing those things, which I couldn't have done two years ago, makes me realise that the limitations I still have aren't so permanent. Ehh, so we don't have the money to travel, and DD wouldn't want to be dragged round the Louvre even if we did. Well, it'll be cooler in ten years' time when she's homeschooling and learning about the history we see; or in twenty years' time, if DH and I escape for a wedding anniversary... or in fifty years' time, when I've accumulated a lifetime of knowledge about ancient Rome and the Tower of London and French cuisine. If I never get to play Cosette (which I don't have the voice for anyway, frankly), well, if I work hard for twenty years I might be able to play Mrs Lovett.
I know it's hard to see when you're in the thick of it, but THIS TOO SHALL PASS. Really. I hope you find peace - it's a hard thing to struggle with.