Get yourself a proper education and then a decent job.
Forget about a glorious life as a mercenary.
If you really want a military career, then become an officer and you will have many options. You will get an education as a leader, which is also highly sought after in the civilian world.
You are still young and much can change for you. Take your school seriously, work hard and the better you cope in school the more substantial your options will be in life.