Swallowing has to do with intimacy. If you swallow, it will make him feel closer to you and more intimate with you. If not, he'll know you have hangups and he'll find someone else.
And don't start making deals like "I'll swallow if you buy me those shoes." He'll see you just want material things and find someone else, who is less shallow. If you want new shoes, get a job and buy them yourself.
I have a long time interest in psychology, specializing in relationship dynamics for 30 years.
(Please note, we give the best advice we can based on the information given in a post. For better advice, please include the age of all romantic partners.)