Morphine and trouble swallowing?

I was recently given morphine for severe pain. I've tried many other narcotics but either they didn't help or had very bad side effects. Now I've been on morphine for just a few days and have noticed that I can't swallow well, especially later in the day as the med 'aculates' in my body. I'm on the immediate release form of morphine. I'm wondering if anyone has had this side effect and if so, did it go away with time or did you have to go off of it? My doc knows about this and we're just waiting to see what happens. If I complain about this much he will switch me to another narcotic and finally I found one that actually WORKS and don't really want to 'experiment' with other meds. I have a *very* good doc so please do not tell me to find a new one. He's very conservative and cautious so it's up to ME to tell him what's going on. Any help regarding this will be enormously helpful! Thanks in advance!