If you're breastfeeding around the clock and not going more than 4-5 hours between feedings, I'd be concerned about the blood + pain (those 2 things together concern me). Especially if you're noticing any sort of decrease in your milk production!!!
See if you can just get in to see your OB or midwife and have them evaluate you - better safe than sorry. The bleeding (esp. coupled w/ pain and definitely if there's any decrease in your milk supply) could mean that you have a small fragment of placenta still in your uterus, and it'd be important to get that taken care of. I had a D&C at 4 weeks postpartum for this, and because I wanted to continue to breastfeed, I explained very politely but very firmly that any anesthesia would need to be breastfeeding-compatible because I was not willing to pump and dump --> I requested a spinal, which worked well for me, and didn't affect breastfeeding at all.
Hope the bleeding is nothing serious, just wanted to encourage you to get it checked out if it concerns you - trust your gut instincts!
P.S. - Congrats on the birth of your first baby!!! :)