You have buttocks and leg pain along with lower back pain. You have two levels of significance, L1-2 and L5-S1. Your symptoms of back and leg pain occur with sitting and are relieved with standing.
Most likely, the L1-2 level is not causing you symptoms. First, there is no evidence of any nerve compression here. The second is you don’t indicate any upper low back pain.
The L5-S1 level is most likely causing most of your symptoms. Herniated discs that compress the local nerve root (in this case S1) will cause buttocks and leg pain with sitting that is relieved by standing and walking. Lower back pain is caused by the annular tear.
A protruding disc with an annular tear is the definition of a herniated disc.
If you have no motor weakness (which would be noted as difficulty walking on your toes), then with three months of pain, if you were my patient, epidural steroid injections and therapy would be the next step in the treatment algorithm.