Brown discharge at 12 weeks pregnant with number 2

Hi mommies.. Yesterday I had a severe left back pain after a short walk. But I didn't felt it like physical pain. It's like gastric pain struck over there. I just rested a lot the whole day. Now today early morning when I used rest room..I could see a watery brown discharge on my panties. I'm really worried. I'm at 12weeks now. Is it normal? #pleasehelp #pregnancy #help