Am I doing something wrong? Tretinoin 0.5%, my skin feels burning

Hi there. I am using tret 0.5 for 2 months now (1 x week then 2 x week) now I am on my 3 month just been few days. However, in the past 2 days, when I apply sunscreen in the morning, my skin feels burning. Am I doing something wrong? I am so concerned and I have a sensitive skin to begin with.