Lower back pain. Things should i avoid.

I've been having lower back pain on left side since September 2017, but it was very mild at that time. I would experiment pain only when i had a very strenuous day. Since December the pain has increased a lot. Now it pains to turn in the bed, and if i walk a lot. There is weakness in my legs, but no numbness or electric tingling. My mri scan taken recently has the following impression 1)transitional element at the lumbosacral junction, demonstrating a sacralised l5 vertebra Please help me understand my situation. Is there a name for it and what could have caused it. What should be my course of action and what things should i avoid. Thank you 2)at L4 - L5, there is mild broad based disc osteophyte complex which minimally compresses the thecal sac 3) Minimal L3 - L4 disc bulge 4) There is no evidence of spinal canal narrowing, neural foraminal compromise or nerve root impingement at any level.