my L5 is compressed and has been manageable. but now it hurts so bad that im unable to attend class. what can i do to relieve th

A compressed L5 disc can be a serious issue.  When you say compressed L5 this could be the vertebrae also.  That would be from a compression fracture and is less common than a disc issue. 

So for an L5 disc issue the best thing for sitting in class would most likely be to wear a back support belt.  Also, if sittong is difficult you may need to move around or stand often.  Let the professor or instructor know and I'm sure they will understand.  Also, with a compressed disc it will show on your mri or doctors report; you may also want to have a medical notice.

Lastly, I would recommend seeing a chiropractor who may be able to help with this issue.  Your primary MD or doc who discovered the disc problem may be able to prescribe an anti-inflammatory or pain killer for the short term also.