Wa'alaikum assalam! Sakit dada at 6 weeks postpartum boleh jadi few things, engorgement, blocked ducts, or muscle soreness dari delivery (especially if you had a tough labor), so it's worth checking with your doctor just to be safe, yeah. A few of us had similar issues dan doctor checked it out cepat je, so don't worry lah, tapi jangan tahan-tahan. In the meantime, try warm compress before feeding and cold compress after, and make sure positioning is comfy when you latch baby. Hope you feel better soon!