Hi, You mentioned that you love the person whom you have been dating for 2 years. While i don't doubt that you do, you need to find a way to occupy your time when you are "feeling lonely" other than "talking to other girls".
This would hurt anyone. Especially if that person loves you too. How old are you? what are your hobbies? what are the things that your friend and you share as things you both like? Why not try doing some of those things together?
Try to involve yourself in an activities that leaves you little or no time for other girls or any other thing that is bad for your relationship. Real friends are hard to find these days, but they still exist. So, when you find someone with whom you would love to spend the rest of your life with, you got to show it in your actions.
Although doing the wrong thing may be easier, the right act yields more positive, long-lasting results.
Stop beating upon yourself, and start thinking on the ways in which you can fix the problem, the first of which is to ask God for help. As you alone can not do it.
I hope you will try and not give up, there is hope still.