I wouldn't start self diagnosing myself with a social disorder yet, if I were you.
If I read you correctly, you consider yourself shy but you are able to interact socially with people and enjoy yourself when you do so, is that correct?
And the major problem you're having at the moment is that your friends must always initiate contact, because you hate calling and suggesting plans?
Let me ask you, are you willing to suggest getting together if you communicate in OTHER ways (instant messaging, texting, letter, carrier pigeon)?
If so, then it sounds as though you just don't like being the one to initiate stuff over the telephone. Okay, so what?
Now, if it bothers you and you'd like to change it; then start small.
Try pretending it's your job. Pretend you are the liasion for the King of Pottsylvania and you must arrange and organize activities on his social calendar. Next week, the King would like to attend a (pick an activity you want to do) with his loyal subject (pick a friend you'd like to do it with).
You must call the King's loyal subject and set the event in motion.
I know that's a little wierd, but it MIGHT help. Worth a try, isn't it?