You and other teenagers are likely to vary in how may friends you have and the type of friendships you have. There is pressure from magazines and television to have certain types of friendships. (Always going out, having fun all the time, being in a group of lively people).
It doesn't usually work like this, or have to be like this.
You may move from being in a group of friends, to being in a close or sexual relationship. This friendship might end and you might become part of a large group of friends again.
Staying healthy can be about being comfortable with the way you are, your friends whatever their number or interests.