Basically all of the opiates work quite well as painkillers and they all have side-effects. But every person is a little different and every one of the opiates is a little different chemically, so every individual has one opiate that will work best for him or her with the most-tolerable side-effects, and it probably requires a little individual experimentation to find out which is best for you.
I know that you've had a terrible time finding a doctor who doesn't think that you are a nutcase because you want your pain treated, but now that you found one you really need to take advantage of his expertise. For example you seem to think that you need to up the methadone dose to what the doctor prescribed. But usually that first dosage level is just the doctor's best guess as to what you need. If you get adequate pain control taking 5mg twice a day then you need to let the doctor know that. Typically when starting pain control the first weeks are experimentation. You find out how much you need to take to relieve the pain. What the side effects are, and how bad they are, and whether they are going away or staying constant. There is a huge variety of things to try, and doing things like using totally different drugs for the main painkiller and the breakthrough drug can really help to keep the side effects under control.
But experimentation implies a 2-way communication. The doctor has to know what the drugs are doing in your body in order to know what adjustments to make, and for the most part the only way that he knows these things is if you tell him!
There is a certain element of fadism when it comes to medication. From what I've heard, the main advantage of methadone is that it is an old drug and out of patent, so it is far far cheaper than it's younger competitors. Of course if you are a drug company and you have the patent on MS Contin then you consider that a disadvantage! ;-) Lin in New Zealand has been on methadone for years, while US doctors seem to be "rediscovering" it quite recently.
You may want to keep a pain journal for awhile. Note the doses and times that you take the meds, and your levels of pain, and side effects like dizzyness and constipation. It really helps when you are searching for that best level of meds which is the best tradeoff that you can have between pain relief and side effects.
-- cathy :-)