When I experienced implantation bleeding with my 1st I was about 6-7 weeks and expierenced light & brown spots of discharge on my panty liners. It wasn't much and it came out from time to time. Probably a total of 4 times. I also got some at 9 weeks that was light pink. Of it seems to cover a whole pad like a period or gets extremely red and accompanied by blood clots and pain (cramps, burning sensation) go to the er as that may be a sign of something being wrong. At any point of expierencing implantation bleeding you feel that something is wrong trust your instinct because when I was 6 weeks and started having the spotting I knew something was wrong beyond just implantation bleeding and I ended up finding out I had a big blood clot on my placenta that was trying to go away!
Apparently spotting is normal for some, if the bleeding is excessive and can fill a pad go to your dr straight away.