I had almost exactly this (brown spotting, more so after I was more active, but no pain). With me this happened between weeks 9-12. I had two early scans during that time that showed that everything was fine. They said it was likely implantation bleeding. I was extremely worried but I'm now 13 weeks and the bleeding has stopped. At one point it got heavier and some blood clots appeared which was when I contacted my midwife and had my second scan, but all was fine.
But I found it really reassuring both times to just speak to my midwife and get her advice, so i would say if you're at all worried, talk to your midwife. It can be very helpful to hear a calm voice in the know.
Fingers crossed it's the same for you and just stops after a while.