Lower back pain since 4-5 months. It?

I am having lower back pain for over 4 mths now. Its a dull ache & it started at left side.The pain is nocturnal & goes away after i exercise & doesn't come back till night. I am very fit otherwise & my morning fitness  includes a 5 min warm up followed by 20-25 min of strength training (mix of calisthenics,Plyometeric) followed by 12 min power yoga and 20 min of rope jumping & finally a 5 min cool down. I also do another 15 min of yoga& a headstand for 2 min in the evening. So, i do all stretches post exercising too I don't feel any pain doing any of these exercises. But the pain has become stronger from last 4-5 days & i can feel it in the right side too. The only thing that has changed in last few days is that I've stopped taking whey protein. However, even when i was taking whey the pain was there at the left side. I haven't had any illness from last 14 yrs except a 7 wks miscarriage 3 mths back.Pain was there before i got pregnant too What could be wrong, how do i correct it?