Hi and welcome!
Let me see if I can explain some of your results to you...as we age, all of our discs will loose some of their moisture , the older we get , the more this will happen. This is what is called disc desication or degenerative disc disease, which is a real misnomer. It is not a disease per se, but a natural part of the aging process for anyone over the age of 21 or so. People see the disc disease and automatically think that this is something to be concerned about. Normally, it is not.
A disc bulge, depending on how large it is , is also most times a normal thing on MRI. It can be positional, meaning, that you could have been not exactly straight, in the tube, which can cause the appearance of a bulge. Even if it is not related to your position, it normally is not of major concern.
Mild canal stenosis is something of a concern, and may be because of the additional stress you put on your back, being in construction and doing repeated heavy lifting. Mild indicates that it is not pinching a nerve or the spinal canal, which is a really good thing.
The steroid injections can help to reduce any inflammation that you may have, and it may be that your back pain is related to your job.
The injections can be a bit painful, depending on how they are done, but it is a very quick pain from the injections used to numb the area they are going to inject the steroids into.
However, the steroid injections can and often do, worsen pain levels for a few days after the injections. This should subside within a few days, and using ice and alternating with heat, plus any other directions given to you by the pain management doctor should take care of any increased pain levels. Remember when using ice or heat, 20 minutes on, and an hour or more off........you don't want to burn the areas by leaving either one on too long.
Good luck and if we can answer any other questions, just ask away.
Sandi