Hello, this all sounds kind of normal. Sometimes bowel movements change as we get older. I wouldn't worry unless you are in pain or there is blood in your stool. The fact that you have been eating more fiber could have something to do with it. Everyone is different in bowel movements. I have been told by doctors and read online that a normal BM can be from once or twice a day, or once or twice every few days. I am not a doctor or anything, but that is what I have been told. Are you in any pain at all?
Then I wouldn't worry about this. Your body is probably just changing. You are in your early twenties now, and you will notice your body changing over the next few years. Its not fun, but it happens to all of us. Keep the appointment with the doc though for peace of mind. There are some gastro issues that cause change in bowel movements so I would still let them know what is going on just in case....you never know.