K.M.
L.,
I feel your anxiety. I have a 9 month old boy and a 23 month old boy and went through the same thing. I joined a playgroup last year with kids closer to my older boy's age and that helped a lot. We meet at a different house each week and the kids can play in a safe area. Often times we met at a local park and that was okay too. My youngest spent most of the time in a stroller, however.
I am not sure where you live, but if you aren't able to take advantage of a playgroup, there is a great indoor Play area in Woodinville called the Tot Spot. They have sectioned off areas targeted for different age groups. You could easily nurse your daugther while your some plays in a safe place. I'm sure there are other businesses like this one if you're not in the Woodinville area.
Wish you the best with your two. It can be a challenge!
K.
Stay at home mom to two boys (9 months and 23 months) and part time children's photographer.