For the past month or so I have been half-heartedly been working out. I say half-heartedly because I do not have the time or the motivation right now to commit to a full schedule. This is relevant because I have not been working out as much as I should or could be to see maximum progress. I am also concentrating more on watching my diet. Now, the problem is that after a workout, I get lower back pain, for a few days afterwards. This isn't ideal. Do I need to stretch more, or perform more back-friendly exercises (there are muscle groups I could work if I wanted to)? I am (a) 17 and (b) not overweight and (c) I don't have any medical problems. It's worrying that I get back pain from what is only a medium-intensity workout. Is this something that will go away with time, or am I doing something wrong, missing something out, etc? Thanks.