You have been diagnosed for bipolar at the age of 14. Rarely this happens and I can understand the problem you are having. You are worried about the reaction of your friends. Your own understanding of bipolar is very important to handle these situations. You would have seen that before being diagnosed you were handling your friends with nothing known about the causes of what runs over you and those why`s are known now. Take this as an opportunity to explain the reasons for your differentness and depression. Bipolar symptoms will recede slowly and by the time you would start to feel better, you will have known a lot of ways to many people.