Alright, so when I put sunscreen on I'm okay. No burning or redness. I've been using it for 3 months so everything's fine. But I find that when I go in the sun for, let's say 20 minutes or more, my face starts buring :-[ and gets a little blotchy. I get out of the sun, then it goes back to normal. Should I switch sunscreens, or do I just need to put more on (higher SPF)? I'm using one with a physical block, SPF 25.