Understand the bad back. Last year was so bad I could barely do anything. Just being able to do 6 miles on a bike is a vast improvement even though I complain a lot about it here. LOL. Over the past couple of days I've had to accept the fact that this what my body says it can do and don't argue with it.
Have you had some PT to keep your muscles strong? I try to keep up with mine, but it's easy to forget. Mine is muscle injury related not disc though so I don't know what treatment you have been doing.
Talk to your doc about riding a bike and take it easy. You don't want to go back to zero and start over. It sucks.
Cycling has helped my back in that I get the stretching I need so it doesn't stiffen up on me. I don't know what bike you have but you might need a comfort style bike that is upright like my DH's Trek Navigator or his Electra Townie. His Townie is amazingly fast despite how goofy it looks. I can't ride them since sitting up straight hurts me.
Hope that helps some.