I have diagnosed severe pain and for years have been on 9 oxy 40s a day with 100mg methadone it manages my pain but my doc wants me on Suboxone now?

Pain vs addiction. Your doctor is rightfully concerned about such high dose. Opioids arent good for long-term management and many became addicted. Suboxone is an alternative maintenance drug with analgesic potential. However, you may better do on Methadone maintenance program.
Reasonable. Methadone 100 mg is a large dose, definately with oxy 360 mg per day on top. Likely your doctor isn't comfortable with the doses for safety issues and wants to rotate opioids. Suboxone can also reverse opioid induced hyperalgesia (extra pain from narcs). I would recommend tapering to at most 1/3 of current doses before trialing a suboxone induction to prevent acute withdrawal.
Should you be? Although that seems like a lot of rx. Many patients can require this amount if they have developed tolerance to the opioids. Your doctor may believe that you are abusing or diverting(selling) your medication instead of taking it appropriatelly. Only you have that answer. What you will have to do is to regain your drs trust. Have your urines not been apropriate or were you caught dr. Shopping?