I understand how you feel. Consider the following:

I have kids, and I feel as if my single friends don't have time for the likes of ME.

I also feel as if my other friends who have kids don't have time to be friends with me, because they all seem to be busy leading their own busy, productive, amazing family-centered, professionally fulfilling lives.

I further suspect that most of the people I know have plenty of social interaction because they have extended family living close by... which I do not.

I remember when I first had my kids, I just assumed my closest friends would take an interest in them, would want to be part of their lives and watch them grow up. To my surprise, the friends who live closest have zero interest in that and NEVER see us, while certain friends who live far away and see us only once a year actually DO have a relationship with my kids and are interested in them as people!

Where am I going with all this... I guess I'm saying don't assume anything about people. Try simple gestures to reestablish contact with a variety of old friends and see which ones "bite." You might be pleasantly surprised.

One of your friends who has kids might be bored silly, wishing s/he could connect with you, perhaps envying your freedom and/or assuming YOU must not have time for THEM.

Another idea... Try inviting a friend with kids on some kind of outing where the kids can tag along... lunch at the park, for example. Kids go play; you get the chance to hang out with your friend; friend is grateful for the chance to have a social engagement without the stressful overhead of way-in-advance planning, rounding up a sitter (which also requires cleaning up the house enough that you aren't ashamed to have a sitter in), etc.

Online dating, I have no direct experience with, but it seems like it's no magic bullet... it's worth a try, but try other things too, like pursuing your interests and striking up conversations with people you meet along the way. I don't necessarily mean "Go join a club!!!" which for many of us is a big BLECH! I mean if you like photography, let's say, take some pictures and when you go to get one framed, chat with the guy at the frame counter...

You are a worthwhile person! Hugs.