Im really worried about some medication that my G.p prescribed for me recently.?

I've been prescribed codeine/acetominophen (paracetemol) 8mg by my gp for migraines, as well as to help calm my severe anxiety, however the medication causes me to feel nauseous and I feel as if the Earth is jiving beneath me : s however I don't feel these symptoms with dihydrocodeine, which is odd aeeing as they are similar chemically. Is it ok for me to request a change in medication in addition to an upgrade to 30mg of dihydrocodeine, because ultimately I am concerned that my dosage approaches the upper levels recommended by the manufacturers, with a higher dose of the d.codeine I will be able to take fewer tablets (it is the codeine which calms both the migraines and the anxiety as I do not really respond to paracetemol) and thus consume less acetominophen which is mustering up the strength to unleash a veritable wave of liver and blood problems later on for me.