Your phone is really messing with your posture. Doctors are reporting that they are seeing a huge number of Millennials (basically, people in their 20s and 30s) suffering from back and neck problems -- problems that they usually see in people twice their age! And it's all because of hours spent hunching over their phones.
Spending all that time looking down stretches the muscles in the back and creates unnatural pressure on the neck, which will ultimately hurt your posture. Beyond that -- if the posture problems don't get resolved, they can lead to hunchback posture and then to breathing problems and even asthma.
Exercise, stretching, and less time hunched over your phone can help.