Ha, I don't know which source I come from, probably just a well-worn and well-used source who has done good things and bad, done things right and made mistakes.
How unpleasant your ex sounds. Being with someone who is openly sleeping with other people can only destroy your own self esteem.
You sound like a very resilient and kind person. Well done for getting back on the horse, in spite of the tricky experiences so far since you started dating again. Personally I think life is too short to be cautious about meeting people. There are so many other things we have to be cautious about (homes, jobs etc) that it's nice to have something to just throw caution to the wind with.
As a man, I find closed women very unattractive so don't worry about putting across the wrong message if you're letting yourself be spontaneous, full on even. It's much better, IMO, to get to the root quickly as the sooner you do, the sooner you know whether there are grounds to go forward. Better that than tiptoing around for five years!
Just never loose sight of your own worth as an individual and don't get involved with men who will play with your self esteem. If ultimately it is a serious monogamous relationship you want, make sure that if you find the man you want to do that with, you both know where you stand and what you want.
Put simply, IMO, relationships only work if both people are in the same place (emotionally speaking) at the same time, and share the same values. If this is not the case, no point in trying to squeeze a pint into a quart pot, hoping the man with change his attitude.
One final thing, if you want to meet a different type of man, perhaps think about different ways/ places to meet one. If you have had a run of meeting a particular type of man who you met in a particular way, mix it up and do something different. Join a class, a club, a charity, a gallery, anywhere where you might meet someone of simialr interests - always the best place to start!!