Hello wrenbird, when you have that hurty feeling, in my experience it usually means i have eaten too much, too quickly. I also don't feel "full" as such but after 7 months i now now when to stop before i get to the stadge that i bring up loads of slime stuff. The eating slowly and small bites is the single most difficult thing i have had to learn to do since the band and even now i still struggle some days.
Also, you have only just had your 1st fill. Many people need only 1 or 2 but some of us need more to find our correct restriction. Keep trying with a whole range of food, eat slowly and carefully and hopefully the hurty feeling will go x