Not sure I can be of help but will give it a try. Our home was built in 1974 and we have a septic system. It has only ONE entrance and that is where we have it pumped out every two years.

The waste goes into the tank and then filters out underground.

I raised three boys here and never had an issue with the tank or the drain field.

I do not know how long you have lived there but if you have not had the tank pumped out, you may be dealing with a drain field that is saturated.

Here is a bit of info from a great website regarding septic systems.

Specifically, this is how a typical conventional septic system works: All water runs out of your house from one main drainage pipe into a septic tank. The septic tank is a buried, water-tight container usually made of concrete, fiberglass, or polyethylene. Its job is to hold the wastewater long enough to allow solids to settle down to the bottom forming sludge, while the oil and grease floats to the top as scum. Compartments and a T-shaped outlet prevent the sludge and scum from leaving the tank and traveling into the drainfield area. The liquid wastewater (effluent) then exits the tank into the drainfield. The drainfield is a shallow, covered, excavation made in unsaturated soil. Pretreated wastewater is discharged through piping onto porous surfaces that allow wastewater to filter though the soil. The soil accepts, treats, and disperses wastewater as it percolates through the soil, ultimately discharging to groundwater. If the drainfield is overloaded with too much liquid, it can flood, causing sewage to flow to the ground surface or create backups in toilets and sinks. Finally, the wastewater percolates into the soil, naturally removing harmful coliform bacteria, viruses and nutrients. Coliform bacteria is a group of bacteria predominantly inhabiting the intestines of humans or other warm-blooded animals. It is an indicator of human fecal contamination.**

Here is the link....https://www.epa.gov/septic/how-your-septic-system-works

Hope this helps!