Legal Resident Status?

I'm having a bit of difficulty here. I am trying to apply for University and I don't really know what to put as my state residency. So, here's the story: in December of 2009, as I was enrolled at Oklahoma State University, permanent resident of Oklahoma since approximately 2003, I left to stay in England for 2 months, and then did a 5 month foreign exchange in Germany. This whole time period isn't really an issue, because I was still enrolled at OSU until roughly July 2010. Then I moved down to Denton, TX temporarily, to live with a friend and earn a little money to try and move back to Germany. I kept my Oklahoma license and tags, but 5 days of the week I lived in Denton, on the weekends I drove back to Oklahoma to stay with my family, mostly my grandparents, whose house I listed for the most part as my permanent residence. So from roughly mid-August 2010 to the beginning of March 2011, I lived 5 days a week in Texas as well as worked there. I filed my taxes, listing my Texas address. Here's the kicker, in March I left for Germany, where I currently reside, but will be moving back in a few days. As far as I'm concerned my permanent residence state-side went back to being listed as my grandparents address in Oklahoma. So now I'm trying to apply for University as a transfer student and I'm not really sure if I'm legally able to say that I'm a resident of Oklahoma, although I will be living and working there shortly. I'm not legally able to say that I'm a permanent resident of Texas, because I didn't live there for a year and none of the bills were in my name. So, the only thing really showing that I lived in Texas are the taxes that I filed, and maybe a library card (with some pricey library fees, so let's not mention that). I know this is all extremely complex, but I would appreciate the help. I can't imagine that I could some how be stuck in a stateless limbo, being neither resident of Oklahoma nor Texas, and I surely can't afford out-of-state tuition in either places. Thanks again for the help!