NHS confusion

[yamikuronue]

 I've been told I can't get help with a certain condition because it was diagnosed in the states before I left. Thing is, I'm staying longer than 6 months; I can't seem to find anything on the internet that says I shouldn't get full NHS care. The only things I've found involve reciprocal health agreements, which seems to apply for students staying under 6 months.

Does anyone know what's up?