Neither of my girls were good sleepers until after 1 year old. I exclusively nursed both of them, and I am on the smaller side, so I didn't have umm... ahem... "ample storage" for the milk. It was very difficult at first, sicne i'd planned to bottle feed, but my first baby rejected the bottles. I'd never been around breastfeeding until I breastfed my own babies. So I had an expectation that they'd sleep through the night at six or eight weeks, since formula fed babies tend to do so. After 12 weeks, I dragged myself to La Leche League, to figure out what I was doing wrong. Some nice ladies at La Leche League helped me to understand the nursing baby works on a different schedule and that since breastmilk is so much more easily digested, the nursing baby MAY wake up more often (not always the case though). Also since I am on the smaller side, I wasn't able to store a lot of milk, so the babies had to nurse more often than someone with larger... umm... storage. And my girls were gloriously fat round babies, so maybe they were just hungry little critters all the time. Yes, I was bleary eyed and exhausted, but we muddled through and I'm so glad we did it. And you're fulfilling more than a physical need during those late nights. They might also just want a cuddle. You can try to give a cuddle but not offer the breast and see if your baby insists on it. You can also try to increase your supply by adding an extra nursing session an hour or so before the bedtime session. Maybe that will fill Baby's tummy up more? And keep in mind, its all temporary. They will eventually sleep through the night, you WILL get through it. In the meantime, get some good undereye concealer for the dark circles, and my iPod got me through it.
Once they start solids, it gets better. Can I encourage you to do extra research on the rice cereal? My info may be out of date, but I thought they were recommending waiting until 6 months, or until the baby can finger feed himself (like cheerios). There was some research that indicated that early solids may cause food allergies. But my info may be out of date, just check it out before you proceed. Four months isn't all that early anyway. Good luck, hang in there. Sleep when you can.