I had a slow start as well, but 20 lbs over the time you are saying is not what any doctor would call good. I don't want to sound like a rebel, but don't forget that you pay the doctor and at some point you may need to say, "I need a larger fill than what you have been giving me."
After my lap band, I felt 0 restriction. After a while, I wanted to see just what I could eat so I went to a buffet and ate like I did before I had the surgery with no problems. Talk about feeling discouraged. I went to my doctor upset...he gave me a fill to 5cc. I was excited...but then again, after a few weeks I felt like I could eat all that I wanted. I went back to my doctor again, they gave me a fill...same thing. I told them the band wasn't working so they said, we'll fill it all the way up then...if you don't feel restriction...something is wrong, maybe band location or slippage, etc. I left...that night I couldn't keep one sip of water down....I went back actually excited as at that point I realized that I just needed to get the band right, but it would work. So...now, I have my band at 11cc's...and that works for me...you may need a lot more fills to get it right.