What are you coding it in?
Stupid question. I remember your other thread now.
Are you using object-based tile collisions? That's a bad idea. You should use tile-based collisions. The sooner you start scripting them, the better, as the greater part of your game will be based on that and once you get that out of the way, enemies will be the only thing left to tackle. If you insist on using objects because tiles seem too daunting for you, use my Ground Object Tiler script. Of course, it relies on a tile layer, so you will need to use tiles with it, but the collisions will all be object-based. You should be using tiles anyway because that's the most sensible way to make a 2D game. My script will just make it run much faster.