Your iPhone is only made for use with an iPhone Headphones which if compared to a Standard Headphone jack are different.
Use the original headphones and plug them into your H/P jack and unplug.
This is a common problem only caused by use of standard headphones.
The iPhone H/P jack has 3 sections, left, right and mic.
You will see on the jack 3 sections.
If you are going to use a regular headphones. you need an adapter.