notanan2 You say that you just bung your blood-stained knickers in with the normal wash, but at what temperature do you wash all these clothes? If I were washing heavily blood-stained items, I would need to do them on a much hotter wash than my usual clothing in order to get them clean.
As Jamilall said, if you are boil washing protein stains you are "cooking them in" so no wonder you find blood stains troublesome.
No boil washing here & no stain issues, however as stated before I wash blood stains promptly so they haven't dried in anyway. Doesn't need to soak out if never left to properly dry in. In a busy family home with usually daily loads in the machine its no extra washing/hassle to wash promptly.
HTH