Had more babies.
I was knackered and hormonal for most of it so the kids watched to much telly and didn't get enough time or attention from me. I regret that, especially for eldest dc.
Now DC are 5,4 and almost 2. I run the house (which is no small task if people are home all day making mess), support DH in running his own business (it's going great guns so makes sense for him to put a lot of time and effort in and it can't be done without my support), do all the cooking, play with and entertain the children, visit family, go to yoga twice a week, garden, walk the dog, read...
My advice is to go for a walk once a day and have some structure to your day. You said you liked reading and going to new places. That to me says day trips to local places and read.
Also agree with posters who said find time for you. It's so important. Yoga, running, coffee and cake, hair cut, massage, walk, shopping, reading in a cafe, nails done, solo lunch, whatever... make time for you.
And read the Happiness Project by Gretchen Rubin. It's excellent on finding your own happy. Which doesn't have to be baby groups!
And also, nicely OP, you do sound pretty down. 