do i need a new septic if i see water bubbling out of the back yard?
Likely. A local septic company should first pump your tank and inspect the balance of your system.
Although normally a sign of major problems, it could be just poor maintenance on the system, heavy loading (too many people and too much water use), or people sending items down the drain that they shouldn't be sending out to the septic system.
You really need to hire someone immediately. If fluid is showing up at the ground surface, it is a health hazard for you, your family, your neighbors, and anyone in the area. Additionally, failed septic systems can contaminate the local water and you could be held responsible for the mess.
Don't neglect this.