✔ 最佳答案
I had this same problem, i am a 19 year old male, i also exercise frequently.
I would hazard a guess that you have pulled a muscle in that area, if the pain is uncomfortable to the point you cannot handle it then go and see a doctor, do not attempt any exercise until then or you risk making it worse.
If you have indeed done damage to your lower back to the point where your muscles are spasming or have tightened then the doctor may be able to prescribe you with a muscle relaxant such as diazepan(spelling may be off), i was on this medication for muscle spasm's for about a week, the only downside to it is it makes you incredibly dozy.
The fact you have had this pain since the morning suggests to me that you damaged your muscle the day before and have woken up with it possibly where it may have tightened during the night.
Hope this helps you.
For future reference consider doing some stretches that work on your lower back, if you are a member of a gym then they should be able to offer some guidance on which ones to do, doing this will limit your chance of injury in future.