In order to be good in a relationship, you have to learn how to be in a relationship. Dating takes practice and most of us don't marry the first person we meet - I think it's a great idea for you to join a group that will help you meet people - when you allow more people into your life you'll learn to trust them bit by bit.
You don't have to fall in love with every girl you date - just go out and have a good time and try to get to know people and you will learn how to figure the relationship part out.
good luck!