I no longer know what to do with my life, any help is much appreciated?

I do believe there must be a huge reason on sudden changes with what you really want. Wanting to join the army, why? If you join the army simply because you don't like going to school is not a good idea. When it comes to choosing the road to take it's very important that you are passionate with it. Because there would be some troubles, trials along the way and if you really love what you do, you'll get through with it. It's hard to live a life with regrets. Those people around you, such as your friends, family, teachers do care for you. And they just want the best for you, try to weigh down and listen their opinions, and of course give them an appropriate and convincing answer to their questions that will make them satisfied. I'm sure they will understand. Don't be to focused with yourself and with what you really feel. Think about others. In that way, it will somehow lessen your depression. Life is too short, enjoy, have fun and go on with the flow. I'm wishing you all the best.