If there's a reason your parents want you to wear a diaper, then that' s fine. Diapers are something very practical, especially at night. Wen you wet, everything stays dry and you can sleep through. Getting enough sleep is something important. That's why it's good that your parents want you to wear a diaper at night. Accept being diapered as part of your nomal routine before going to bed and that a diaper always belongs under your pajamas.
There are many older children who still need to wear diapers. You are not alone. Our boy wears them during the day and night too. For him, wearing a diaper under his pants or pajamas is something normal. He needs that extra protection and is completely unconcerned about it. We also still have a changing table and blog about it:
https://tobischangingtable.wordpress.com/