Messages disappear from lock screen

Since I have updated my iPhone 7 to iOS 11, my text messages disappear from the lock screen notifications after a few minutes even though I never unlocked my phone. None of my settings have changed, the text will go off, show on the lock screen, repeat after 2 minutes, then will disappear shortly after. If I check my lock screen at times I will think I have no new messages but open my phone and they are there unread. Before the update I was able to swipe down on the lock screen and see all unread messages. With the new update swiping up to the “Earlier today” does not show the messages, even though I had never opened my phone since getting the messages. I called Apple and representative was not able to assist me.