How to use OBC quota in Assam if OBC certificate obtained in Bihar

hello..sir..i want to apply for state and national competitive exams for doctors under obc quota but the problem is i have obc certificate from my ancestors state 'bihar' under mallah caste (my surname - sahani) and my family never resided in bihar,we actually are living in assam for the last 40 years and hold a permanent residence certificate of assam. i did my class 11,12 and mbbs from assam only,my father did class 1 to 12 from here only. Am i eligible to avail obc reservation in assam? if not then how can i avail the caste reservation in assam as i am not eligible to get obc reservation in bihar also since i have not done any schooling or mbbs from bihar? i feel very disappointed of not been able to utilise the quota when i certainly belong to it!(p.s. none of my parents or siblings have used any quota before we applied always under general category).