First, its a growth spurt. My 6 month old went through those where I was worried I'd never get a break! It only lasted for a little while, so there is light at the end of the tunnel.
What I did was add 1 bottle of formula a day to give me a break. I didn't start cereal until 4 months, and then it was just a little bit at dinner. Once the cereal started, she slept like a champ, I was actually waking up wondering if something was wrong with her. I was also used to breastfeeding in the middle of the night, so there were times where I pumped to releave the fullness. Then, I got a head start of the next day plus she was full and happy. I hope this helps. Hang in there!