can’t download large files in mobile network

I've been using Lumia for over an year. I used to download all the apps using mobile data and have never ever used Wi-Fi. But now, when I tried to update Watsapp, it doesn't gets updated and says it requires Wi-Fi. And from then all the new apps says it requires Wi-Fi. I don't have access to Wi-Fi and i don't know what's the sudden problem in my phone, please help.. I'm getting frustrated..