Yep, I am just getting back on my bike after being off for the last 6 months with a significant buldge in L4 and I also have a small tear in the disk that is leaking disk fluid (don't remember the name). I did the same things you are doing. Lots of physical therapy and I had a steroid injection done by a pain clinic. This is my second steroid injection and they seem to work pretty good at bringing down the disk inflammation and reducing any stenosis that you might be experiencing.
Last year I also had a significant buldge in my C6 (neck) that brought on a lot of stenosis.. Lots of left arm pain. Very nasty! I had a steroid injection there as well and it cleared up.. Although a I have started to feel some symptoms of arm pain again but they are sporadic and do not last long. If I get it back, I will go in for another steroid injection.
All in all, I have missed 6 months of in season biking over the last 2 years and I went from trying to get into racing to just trying to get a full season under my belt! I also changed my bike to get a longer head tube (still with a full spacer stack) and I also went to a Fizik Aliante saddle to push my pelvis more forward to keep my lumbar region more straight. Lastly, I have went to never stretching at all before or after my ride to at least 15 minutes of good stretching before the ride and 20 to 30 mins of stretching post ride. It is a lot more maintaince, but if you really want to ride.. Well you gotta do what you gotta do.
Good luck friend.