Trog, I'd like to challenge an assumption of yours--that only a long-term relationship, one that lasts the rest of your life is a successful one, and anything else is a failure.
... .the truth is, I really loved the affection and I guess I just didn't want to be alone anymore.
I don't think there is anything wrong with that motivation to be in a relationship.
Did you mess up some other things in this rebound relationship? Yes, and you already identified many of them. Go ahead and learn from your mistakes, and try to do better next time when you are ready to date and look for a relationship.
Short-term relationships can be good, healthy, fun, and end when they are supposed to end. Especially if both partners are honest about the lack of a long-term future in the works.
In this case, you weren't ready for a stable LTR. Neither was she ready for a stable LTR, from what you say of her. Neither of you were very self-aware about it, and neither of you were able to be honest with the other about what you didn't realize.
That's all interesting stuff to think about, but doesn't answer your big question: What now?
Suggestion #1: You don't sound ready for a LTR today. Don't chase one actively right now. If you aren't comfortable looking for a STR, casual dating, or something of the sort, taking time out may be your best choice.
Suggestion #2: Build the non-romantic part of your life into something that is rewarding and wonderful while you wait on the romantic part. Do you like your job, your home, your friends, hobbies or other activities, etc?
Q1: Do you see parallels between the problems in your long marriage and the problems in your last r/s? Or aspects where your exgf is like your exwife?
Q2: Did you fall into unhealthy patterns again, and if so, did they predate your marriage?