Okay, here goes...
I've had 3, expecting 4th, successfully breastfed the first 3 for 13-14 months each (which was my goal). Had all three sleeping through the night (which I classify as at least 6 hour stretch of time) by 7 weeks of age (and 10 hour stretches by the 4 month mark).
Here are my suggestions to you.
1.) I would suggest that you get a schedule put in place. It is possible that your baby is snacking. If he is snacking, then he is only getting the foremilk (the watery milk that only helps with thirst) and not getting the hindmilk (the fatty milk that helps satisfy his hunger). Your goal needs to be to get a full feeding in each time you nurse him.
My schedule for each of my kids at 6 months of age was as follows:
Nurse at 6:30am, 9:30am, 12:30pm, 3:30pm, 5:30pm, 7:30pm, *sometimes 9:30pm, sleep through the night. Notice the cluster feeding in the evening...that is to help prepare for the night ahead.
Many times breastfeeding moms (not saying you're doing this) will start to stretch out those daytime feedings, and it ends up being at the expense of night time sleep. Get those daytime feedings more on a schedule and see if it helps!
2.) You may not be a fan of the CIO method, and I get that, but I would also encourage you to read up on the different sleep stages for an infant. It is quite normal for a baby to cry out between sleep stages. If you go in and get the baby, you may actually be waking the baby up without realizing it. We think crying means the baby is awake...when in actuality, the baby may be transitioning to that deeper stage of sleep that he so desperately needs. I have posted on this before (feel free to read some of my other posts). I would strongly encourage you to wait for 5 minutes in the night before you go get your baby. You may be surprised to see that he falls right back to sleep before the 5 minutes is up. Keep in mind that 5 minutes in the middle of the night seems like FOREVER. Look at the clock. Quietly wait. See what happens.
Please, please, please, try some of these suggestions (or other suggestions if you feel more comfortable with them). You absolutely need to do this for both you and your baby. Sleep is so incredibly important for both you and baby!
Good luck with things!