Laymen symptoms and conditions

I was on toprol-xl for almost 8 years without many problems. i also take isosorbide mononitrate.A few months back I was switched to the generic version (metoprolol succinate er by sandoz) now i have many problems.First I have to say I am disabled with severe COPD. Although I do not feel depressed I have a lot of symptoms of depression. Remember I had no symptoms what so ever until switched by Walgreen's or HMO or Doctor to the generic version. Not sure what to do I have a doctor that does not truly listen,plus he did not want me on toprol xl to begin with. Even though it was good for me. Good luck people!