Yes, this is normal. The main thing is that you keep the areas where he regurgitates clean. You can take the bell and other toys he does this to away, but he will find something else like a perch or the bars of his cage.
It is still the Amazon breeding time for most areas in the US so he will probably continue to do this for a bit longer. By fall he should be over this.
If not, your enviroment is causing him to stay hormonal.
To bring him out of hormonal behavior, cut back on the amount of light he receives. He should get a minimum of 12 hours of complete darkness. This is not for getting more sleep but to slow down the production of hormones. You may have to go up to 14 hours of darkness to bring him out of this.
Joanie Doss
The Amazing Amazons
Amazon Parrots - Joanie Doss - Intro / Bio