How Dirty is Too Dirty?
Yeah, it does feel kind of yucky pulling up your pants after you saw your pad is slightly soiled. On the other hand, you can’t change your pad for every little drop of blood. So, it depends on how badly it is soiled really. It’s like deciding if you want to wear the same shirt twice or put it in the washing machine after you have worn it once.
As a general rule of thumb, in order to prevent infection (and general yuckiness), women should change their pad at least every four hours, even if there’s only a little blood on it. It’s really recommended not to walk around with blood on your pad, even if it isn’t leaking yet.