Since your doctor didn't see any indication, you don't have to worry about that. People who are extremely near-sighted are prone to detached retinas. People can get floaters at any age. Sometimes they can occur from violent activity, like playing football. In most cases they go away in time, but the larger the floater, the longer it takes to dissolve into your system.
Floaters sure can be a nuisance though, especially when they get in the line of vision.
After a while, they float over to the side. There is nothing you can do about them but to accept you have them. The worse thing you can do is to let them bother you. The more you concentrate on the floaters, the more you will start to notice them. Notice how you can tune out many sounds unless you really start to listen for them.