Carolyn, it gets easier! Or at least, the logistics of getting out the house do! If you have a moms group or a local homeschool group, you'll find they will often have park days, and plenty of moms available to help hold babies and wrangle toddlers. They will also have older girls who will be happy to babysit, or even just come help you do stuff at home, or help you on an outing.
Actually, that's what I'm doing this weekend. My 11 year old's religious school class is leading services Sat morning and my husband will be away. Sat morning services are long -- more than 2 hours -- and there's no way my 2 year old can sit through them. I'm bringing a 13 yr old with me, who will be able to take her out for a walk, a snack, a story, or whatever.
Anyway, I also left a pretty dynamic consulting job to be a stay at home mom. I haven't missed work yet, but I do miss the freedom, the independence, and the money. Still, I think it is a huge privilege to be able to stay at home and raise my children and homeschool them. Sometimes I feel really constrained, but mostly, I love it!