Lower back pain

I need some advice from experienced mommas. I'm a FTM and have been healthy and active my whole life. No major pains or issues with any part of my body.

But now I'm 21 weeks pregnant and I've been having constant lower back pain mainly on my right side. It's worse when I'm walking and if I move just right I get a stabbing pain. Any advice on what to do to help alleviate the pain? I want to stay active during my pregnancy but the constant back pain makes me nervous that I'm going to just injure myself more.

FYI Im 5'5" and currently weight 127 (pre-pregnancy weight was 120) so I'm not overweight at all.

Has anyone else had similar pains? If so, what helped?