Leg cramping?

I am almost 10 weeks pregnant with my rainbow baby, and am experiencing lower back pain that radiates down my bum into my legs. It hurts like hell, especially when I am trying to sleep. Most the time its at the back of my legs, just every now and then down the front. It is really uncomfortable, especially after hubby and I went for a walk with the pups. We did a 5km fun walk last night with the pups. Not sure if the leg cramps are normal, but heard baby’s heartbeat on the doppler tonight, which puts me at ease. Your thoughts? Anyone else experiencing leg pain?