Really bad rash from sun

j

I am in mexico and I have developed a terrible rash on my thighs and stomach, the last two years that I have come to mexico I have gotten it. I never used to get it this bad at all. Can it have to do with my sunscreen maybe? it’s not very itchy really. It’s red and huge. Is there anything i can do to prevent it or get rid of it for good. please help