2D Game Mouse Problem

Hello guys, i'm making a 2D game, and i got a mouse problem. first, see the script below. it's enemy's script.

void OnMouseDrag() { Hp-=5; } void Update() { if(Hp<=0) Destroy(gameObject); }

This means when my mouse position is inside of enemy's box collider 2d(i'm making 2d game) and if i'm pressing mouse button, then enemy hp is going to be decreased until i stop pressing button, right? so let's say mouse is inside of enemy's collider and i'm pressing mouse button. after some time has passed, hp is less then 0, so object has been destroyed. after that, with mouse button steel pressing(i mean steel firing), move my mouse pointer to another enemy's collider. but second enemy got no damage until i detach my finger and re-press button. what should i do in this situation?

sorry for low level English, i'm not a English-speaking country's people. so please use easy words and if you can.. excepting you guys help.