Most people dont realise how little blood it actually takes to soak a pad. Of course all pads are different but try it sometime, measure about 20mls ( add a bit of food colouring to make it easier to see) and pur onto your preferred type of pad and see what it looks like. Repeat this until the pad is soaked, I have actually done it with blood for an educational tool for midwives, to estimate blood loss following birth and was surprised how little it was.
The time you need to worry about how much blood you have loss is if it compromises how you feel. If you are feeling dizzy then you have lost too much and need to see a doctor ASAP. If you are feeling tired and run down then you might be anaemic and need to have your Hb and iron levels checked. If its just annoying but you feel OK then your body is coping with the loss and will replace the blood over the next few weeks. Think about blood donation they take 500 mls or so out without it being a problem every three months and belive me if you saw that much blood spread out it is big pool.