Why does my iPhone screen dim when I send text messages?

Whenever I'm texting someone and I tap the voice button to use talk to text, the screen dims to black on my 5s, if my face gets close to the phone.

Also, if I put the phone up to my ear or near my face whenever I have text message convo window open, the phone beeps and dims. It starts trying to record a memo or something?

I'm jailbroken and I have never seen this happen before. Any ideas on what is going on?

Would appreciate any help! - bud