There is a sewer smell in the bathroom in the back of the house seems like it is coming from the drains, also the other bathroom tub was not draining for months and now is draining can this be connected what could it be?

Sounds like you have a blocked vent stack which can cause trap to siphon and let sewer gas into the home. Rod the vent stack from the roof with enough snake to reach roof top to basement plus 20'