Sarah, we are almost the same age. I find that it's hard to meet older moms.
I have been really lonely the last couple of years--as we are new to the area where we are now living. But after a while, you get used to it--I know, it does sound odd. But I really find myself so busy with every day life that I am not feeling that as much any more.
I used to force myself to talk to anyone with a kid in tow--at the store, at the library, at the rec center, etc., and eventually I made some friends. It almost reminds me of dating--and trying to meet someone. You have to really be on your best behavior and all that, just to meet others.
I have one really good friend now, but even that has its drawbacks because she has a lot of drama in her life. Even though we are close in age, education level, and our kids are close in age (both in our 40s, both PhDs, both with toddlers)...but even with all that in common, it's not that easy lately.
Some other things that have really helped me--taking a class when I can, reading when I can-- and exercising--that's been really helpful. I run with my kids in the stroller.
Look into things that you have always wanted to do, but couldn't do due to money, time, etc. and just read up on and even make a plan as to how you would like to do it in the future. Your kids won't be little forever and eventually you do get parts of your life back. When they are toddlers or babies, being a sahm is all-consuming.
I have always been really interested in falconry (spelling?) and plan to look into hopefully taking "a class" or lessons, or whatever it takes to work with birds of prey. Maybe I can even look into birds of prey rescue.
I think as my kids get a little older, I also get more "into" their lives and that makes it less lonely.
I know this is hard to do--but if you can really focus on the moment and be really present in what is going on, the loneliness really does subside, even if only temporarily.