It was raining, my phone was in my coat pocket, water got into the headphone jack and now it's stuck in headphone mode.
I've tried blowing air into it, cleaning it with a q-tip, unplugging and plugging in my headphones several times, turning my phone on and off, but nothing has worked so far
Read more: https://iphoneus.org/faq/got-headphone-jack-wet-and-now-my-iphone-is-stuck-in.html