Hi Elizabeth, welcome
There are a lot of people here with all kinds of struggles, many probably similar to your own, so its a good place to vent/share/support.
As for motivation, if I were you I'd look at that fact that you KNOW you can lose because you've done it. Sure you gained some back, but there's no use beating yourself up over that. You know you can do it now because you've already done it once
We're not so different really. I'm 44, single, no kids with nieces/nephews. I don't remember feeling overweight as young as 10, but maybe from about 14ish. I've never been the small girl in the bunch and for decades I told myself I was just meant to be big. That gave me permission to eat horribly and a lot! Why not? I was going to be big anyway, I might as well enjoy myself right? Then 6 months ago, I finally reached the point of "that's enough" when I was *this* close to hitting 300 pounds. That 300 number freaked me out enough to snap out of it and make some decisions to get healthier. Not thin or skinny - healthy. And now, 81 pounds later, I still have a ways to go, but I AM healthier and I AM stronger, though I'm not thin/skinny. I don't think when I reach my goal weight of 154 that I'll be thin, but I'll be fit and that's my ultimate goal.
Take a look around the forum threads. There are some good ones if you're looking to find people at your stage of the process or maybe to find ideas of how to alter your eating to fit your needs. There's no one answer for everyone, but there are a lot of things to try to find what works for you.
Glad you're here
Laura