I actually had two bleeds, one at about eight weeks and one at about 12 weeks. I know exactly how you feel, it is the scariest thing ever.
My first one, I was literally walking to the clinic for a private reassurance scan since our dating scan wasn't until 14 weeks (due to travel). I felt a huge gush and my jeans were a mess. We went and got a taxi and sitting in the waiting room was the worst experience, since I had to have a full bladder so couldn't even go to the loo to check myself. Thankfully, there was a heartbeat.
The technician doing the scan said she could see a 'pouch' of blood on the monitor and that she reckoned my implantation had caused a sort of blood blister that had just now decided to burst. Which made sense. There was no pain.
My next bleed was even worse, more of it, more red and came with an immediate feeling of nausea. For that one I was in an airport in Colorado on my own, trying to sort out my cancelled flight. I was at a very high altitude and dehydrated (which I think could have been a factor). I went to the loo and cried, but I didn't go to the hospital because it was the same as before, gushed but no pain. I told myself if it kept on, I had pain or I had clots, I would go to A&E. But I wasn't keen to have to deal with the horrific American medical system.
Also, I should say, I had days of light brown streaks between weeks seven and 16 or so, but I never took this as a problem, it seems common.
At our 14 week scan, everything was perfect.
So, it happens. I've read about women that bled nearly every month and had a healthy baby. I think the red flags are any sort of pain, and heavy clotting. Also, prolonged bleeding. But of course, if in doubt, go to hospital.
Good luck, I know how completely terrible and demoralising it can be when it happens, I hope it doesn't happen again. I'm nearly 21 weeks now and no more bleeding. Hopefully it's smooth sailing from now on for you!