I took all of my things over there.
Where did you take your things?
I must say it then. I moved in together with my girlfriend.
If you didn't ask to move in there first then that was a bad idea. A couple should talk about moving in together before someone imposes themselves.
Her place was bigger and I made that decision without her because I need as much room as possible and she might not have let me.
If you need more space, you should have spoken with her first. Then you could have decided together to move into hers or moved into another place together. Now she might resent you for imposing on her.