Help with iMessages and normal SMS

Hi everyone. I have bought an iPhone 11 Pro Max approximately 3-4 months ago. I have noticed that my text messages are somehow being wiped out on the screen (quite literally). It’s not just from messages from a while ago, but as I send new messages they start disappearing. I have attached a screenshot as it’s difficult to describe. I have blacked out some personal information but you can see in the red circles of the disappearance. Please help me.