I have the exact same injury in my lower back. I am just unsure if the discs are the same. Anyhow when younger I had to sleep on a very bad bed which started causing me back pains. Later I started deadlifting and that expanded the pains to protrusions. Doctors told me that everything began with the bad mattress.
So number 1 thing for you is to make sure the mattress you are sleeping on is good for your back. The harder the mattress, the better for your back. Also when you sit down on a chair it's good to have something against your lower back so that it is resting.
That's what doctors told me and that has worked for me ever since. However they also told me to stop all back exercising otherwise it will lead to disc herniation. I did not do anything for 2 weeks to see how that's going to go and also I wanted to think things through.
The pain in my lower back would not go away. I figured that the muscles of my lower back would just atrophy if I don't work them out. That's bad since your muscles support the bone structure of your body. Hence I started working out again keeping several things in mind.
1) Any more serious pressure on your spine might lead things to herniation. That's why I replaced weights with rubberbands. I will give you an example why. Imagine biceps curling. I would curl with barbell of 50kgs. My set would be around 40seconds-1minute. During this minute the barbell would remain in my hands and for the whole minute my spine would have to cope with 50 additional kgs. And biceps are one of the smallest muscle groups in the body. I would use much heavier weights on other exercises. When using rubberbands, however, every time I go down, when curling, the bands will release the pressure on my spine. So if I am to go for 10 reps, at the end of every repetition my spine will be completely relieved from any pressure. If interested check bodylastics, I have been using them for around 3 years now and am highly satisfied: http://www.bodylastics.com/
2) Even with rubberbands however the pressure on my spine would still be a lot. That's why I replaced the position of the bands. For example instead of doing biceps curling having the bands below my feet and pulling them up, towards my shoulders, I would attach the bands above my head and pull them down behind my head. This way the bands' resistance is pulling my body up instead of pulling it down, putting pressure on the spine.
3) Bands and weights are different. I can't maintain enough strength just by using bands. That's why I focused more on body weight exercises, such as back lever and front lever(Disclaimer: both articles are written by me). These really, really strengthened my lower back and increased the size of my back.
4) Sometimes I would feel a discomfort in my lower back, typically at the end of a harder workout. The feeling is as if somebody has pressed me against the floor. So I would just feel my lower back heavier somehow. That's when I would throw some spinal extensions. There are two exercises one of the best gymnastics' coaches in my country taught me. Focus on the first exercise, I have linked you directly to it. Some of my friends have similar back problems and would refer to this exercise frequently to release the pressure from their spine. Here's the link: http://youtu.be/tVokXmC6eJM?t=33s (Disclaimer: This video is mine)
Also never forget to warm your back before a workout. Be careful with the warming up though, anything more aggressive might provoke a hernia. I hope this helped you, if you have any questions please let me know.