bleeding in 9th week

As some of you may know, i went for a ultrasound check at 7th week but all we saw was an empty sac. They told us to come back 2 week later on the 19th Aug. But today, at 9weeks and 1 day, i saw blood from my pantyliner.. I read that it's normal for some as long as it's not heavy but should i still be worried?