How to import from blender with a collider?

I made a room in blender, and i want to export it to unity. I exported it as an obj.When i imported it into unity and walked into it, i walked through it. I do not want to add 100 different box colliders to small objects, so is there a way to export/import it with a collider already on it?

ps I am not a pro at unity. If its something complicated please explain it.

First of all, the best way to share a model form Blender to Unity is using the fbx format. You can export to fbx from Blender and configure what and how to export (you will miss this params if you paste the blend file directly to your unity project).
After exporting you put this fbx file in your assets folder and when you select it you will see a lot of configuration settings in the inspector panel related to the fbx importer of Unity.
In the first tab of this panel there’s a check to tell Unity to generate colliders for the imported objects. This will attach a mesh collider to each imported object. This is far from being optimal because mesh colliders are expensive and you may use them only when you really need accurate collisions, instead you can use simpler colliders as boxes (for example with tables or chairs).

Try using mesh colliders,if objects in your room are divided combine them and then use mesh collider.