When I was a teenage girl I would mess with my boyfriends
Why would you mess with your boyfriends?
It was fun to do it
You should never mess with people for no reason. You were being disrespectful to your past boyfriends and should be kinder towards people who care about you in the future.
I'm too big of a bitch to be kind towards anyone.
This is not an excuse for the way that you choose to treat people.  When people care about you, you should treat them with the same level of kindness that you expect for yourself.  It's not only the right thing to do, but it will cause people to be kinder to you in return, which is worth the effort.