The decompression exercise seems to help a bit, even more than you thought it might. You want to accelerate the healing (i.e. eliminate pain) now. It's time to begin gentle stretching moves. You'll want to tie this into the decompression exercise as well, doing the stretches after the decompression.
Stretch #1 - lay prone (on your back), and pull one knee to your chest, holding the knee with both hands. This is a very basic hip/lower back stretch. Hold this stretch until you feel the tension in your back subside. Why do I say this? You will notice that the typical 15 -30 second hold you hear about so often does not apply to you because in that time period, you will notice that your back is still tense. Think yoga here. Slowly pull the knee as far to the chest as you can, and try to relax your lower back as much as possible. Wait until you feel it "give" before you end the stretch. Repeat with the other leg. You start this stretch in that sit-up position you had for the decompression exercise. When you're ready to advance the stretch, just extend one leg out while you're pulling the other knee to the chest.
Stretch #2 - lay prone, and pull both knees to the chest. The goal here is to get the hips off the ground. This will be difficult in the beginning because the lower back muscles won't want to release enough to allow that to happen. Keep working at it. The same rule applies here as to the length of time you hold the stretch.
These two stretches are the ones you will get if you go to physical therapy. You can do these on your own very easily. Get in and out of the stretch positions the same way I told you to get in and out of the decompression exercise.
Stretch #3 - More advanced. Sit on something soft, like a pillow (Bosu, if you're in the gym), and spread your legs as wide as you can. Reach forward as far as possible, making sure to support yourself with your hands by putting them on the ground. This stretch will focus on both your hamstrings and your lower back (a good combo since both tend to cause back pain when tight). Hold the stretch as long as you want, sticking to the rule on length of time for holding the stretch. By the time you're able to do this stretch, your lower back muscles will release, but they will be tender, so returning to your starting position must be done slowly. Your muscles will thank you for it. After going down the middle of your legs with this stretch, try reaching out over each leg, putting one hand on either side of that leg. Move to the other leg, and then finish back in the middle. Do not fight this stretch! If you can't reach the ground with your hands, then it is too soon to do it. You may try this stretch with assistance from another person, but make sure that person knows what he or she is doing!
Stretch #4 - More advanced. Lie prone, pulling both knees to your chest. Kick one leg out straight and rest it on the ground, while holding other knee to chest. If you have your left knee up, drop your left hand off that knee and lay it on the ground, straight out, palm on the floor. Use your right hand to pull your left knee across your body as far as possible. The goal is to get the knee to the ground. Start by trying to get your foot to the ground. Breathe out and relax as much as possible as you rotate over. You will take somewhat more shallow breaths as you rotate further, but keep focusing on relaxing your lower back with each exhale. Do not be afraid if you feel a "pop" in your lower spine. That's just your verterbral joints releasing from their compressed state. This stretch should not be attempted until you can roll your hips off the ground in stretch #2. Important: After you stretch to one side, pull both knees to the chest to realign your spine before stretching the other side.
Stretch #5 - More advanced. Sitting in a chair, or on a bench, cross one leg over the other so that only the ankle of one leg is resting just above the knee of the other leg. Sit straight (neutral spine), and push down the knee of the crossed leg so that it is parallel to the ground. If you can do this, then while holding that position, lean forward as far as possible keeping the neutral spine (do not round it yet). Hold this position for about 1 minute. Then, relax your spine as much as possible, rounding it, and reach over the crossed leg with both hands like your trying to tie your shoelace on the shoe of the supporting foot. Repeat on the other side. Do this stretch twice each side. This stretch can be done as often as you'd like, and I highly recommend it!