Hi mama! Implantation bleeding is normal talaga, usually light spotting lang na nangyayari around 6-12 days after conception, so it's possible na yan ang nakita mo, pero since you're already 4 weeks, best to confirm with your OB kung ano talaga ang spotting na yan kasi may iba pang reasons din puwede mag-bleed in early pregnancy. A few of us went through the same worry, and honestly peace of mind lang talaga sa doctor check, especially ngayon na may spotting ka na, kaya sched na if you haven't! Congrats on your pregnancy, mama!