I have two bad disks in my lower back (L4 & L5) that were nearly blown. I too have always been very active. However, I've found riding helps my back - but there are some things I have learned that may or may not help, and some things that echo what others here have said:
My handlebars cannot be lower than my seat, and I spend more time in a more upright position - I'm only just now fairly comfortable with my hands on the brake hoods, and I only spend a few short minutes at a time in the drops. The injury is 3 years old now and still creates problems from time to time, but I've learned I must take my time with EVERYTHING.
If a more upright position helps, you can get a hybrid and put road tires on it. Or, I know a number of people who have bad backs and ride recumbent bikes now.
Someone else said core strength - absolutely work the abs. I hate ab work, but I make myself do it at least once a week.
The suggestion of getting a physical therapist to have a look at your position on the bike is an excellent one. I recommend PT for anybody who's had a debilitating injury, without the guy I had, I don't know if I'd be on a bike at all yet.
Most of all: (((hugs))). I know what it's like to lie there in pain, crying and wondering if life will ever be normal and let you do any of the things you want to do without hurting so much.