Unfortunately, it isn't easy, or necessarily appropriate, to expunge the undesirable portions of our medical and psychiatric histories from our records.
Your suicidal gesture, though regrettable, is an important element of your psychological history. Sometimes certain parts of your medical history can be compartmentalized and excluded from examination by specific parties, but many organizations require that you sign documents allowing them to peruse the entirety of your records. (you can understand how this would be important to the military, where you will be asked to handle weapons and participate in highly stressful activities.)
your best course might be to see your own physician to discuss the nature of your suicidal gesture (this discussion, too, will become part of your permanent record) and to undergo an evaluation to confirm your stability.
I hope things go well for you. Good luck!