I also breastfed and coslept with my daughter. She didn't start sleeping through the night until she was 15 months old. She was waking up every 2-3 hours to eat until she was about 6 months. Some babies are good sleepers and some just aren't. Mine wasn't and it sounds like your baby isn't either. You just have to find ways to rest the best you can. Since you cosleep, do you nurse her while lying down? That always helped me. I could rest a little while she ate.
Also, a lot of people say to change the diapers after they eat, but I always changed her first. She would usually calm down when I fed her, but if I undressed her and changed her diaper, she would get upset again.
Also, are you living with a husband or partner? If you are, get him to help. I would always pump before I went to bed (mostly because it kept me from leaking at night) so I would have extra milk. I would freeze all of it but 2-3oz. He usually woke up at 5 to go to work, but we had a rule that any time after 4:30 that she wakes up, he needs to go heat up a breast milk bottle and he did that feeding. That way, say she wakes up at 2:00am, then wants fed again at 4:30, then again at 7:00, you get to sleep 5 straight hours. Since we have the typical household where he is the main provider, he was still well rested for his job since I got up the rest of the night.