Well, let me congratulate you because you've given the first step which is to accept you have a problem (I don't think it is a problem, but an imperfection: Not the same! ) and you're looking for help.
Being flirty and fun doesn't mean you'll always be flirty and fun. There are times you can be flirty, fun, happy, and easy going, but there are other times when you must be hard on your decisions. Finding the balance between being flirty and having strong decisions and sticking to them is the perfect spot.
When you get into another relationship (Do not rush it! give yourself some time: Nikki's time! ;) ) talk about it, ask him whatever you can change for better, and if he really cares about you, he will be sweet but he wil tell you. Don't be afraid to talk! Most of the times, break-ups happens because we never talk. That is depressing, isn't it?
Nikki, I wish you the best of the lucks, and even though I doubt I was helpful at all, I hope you enjoyed reading my post. :D
-Jean.
