It can be so challenging to try to get through the day on very little rest! It can also be so hard to find patience at night when you are so worn out from all that you and your family are going through!
Hang in there!
Your little one is still *so* little! I know it's easy to remember how easy it was with your first, but also remember that they are two completely different people, and they each have their own, unique perception of reality. When we compare children, all we do is put unrealistic expectations upon them, and we also set ourselves up for disappointment when our children don't live up to our expectations.
Honor your son's uniqueness, and be willing to meet him where his at right now, in this moment, without regard for what any other child at this age might be like. Your son is telling you something loud and clear. You say you want him to learn to sleep on his own...that you are okay with the cry it out method. I really beg you to think more deeply about this, and whether you want this to be your son's experience, and whether you want this to be the foundation of your relationship with him. I would also suggest reading the continuum concept and dr. sears' nighttime book (I'm not sure of the exact title).
It could be a health issue, it could be allergies (this is a really big indicator of allergies! We went through this with our little ds), or it could just be his personality! You said he sleeps really well during the day. He may not be used to sleeping at night, as his rhythm inside you was probably to sleep during the day while you were on the move, and be up at night while you were sleeping. Six months isn't really a long enough period for a lot of children to be sleeping through the night on their own. A lot of times, when people say 'sleeping through the night' they mean a 4 - 6 hour stretch...not from 6pm to 6am the following morning. Perhaps he's a night owl. Like it or not, your son has his own internal rhythm, and it may or may not be in synch with yours.
It doesn't sound like you are co-sleeping. Have you given this some thought? Babies (especially one so young and extremely dependent) need a LOT of closeness and comfort. Even when they are crying, *especially* when they are crying, they need that connection. Our son went through a spell of crying a lot in the night...we NEVER left him to cry...we stayed with him, laying with him, rubbing his back, reassuring him that he was loved and we wouldn't leave him.....that no matter what he did, we were going to be there for him. Not to say there weren't moments of frustration and even anger or resentment. But we tried to live up to our ideals and act with regard to our values as often as possible.
Babies don't always nurse for hunger. They also nurse for comfort, especially when they may not feel totally secure or comfortable. This is normal, and it is perfectly fine. It is not indulging, it is not spoiling, it is giving your child what he needs. Meeting a child's need for love and affection will not damage him. You can never give a baby too much love.
One more thing that just came to mind that a good friend of mine told me, who has worked with lots of babies who have nighttime issues, is that some babies who are up a lot at night are babies who are not engaged enough during the day. This is not based on any sort of chart that tells you how much attention/interaction a child needs per day, this is based on your particular child. Each child is different, and so will have varying degrees of need.
You will probably get many responses telling you that many mommas have experienced the same thing. This is because it is normal. Again, I will say...he is SO young! It's up to you how to deal with it. No matter what you do, it will get better. Some ways make take longer than others, but those same ways that may not yield immediate 'results', are some of the ways that really honor the bond and connection between you and your baby, and really focus on meeting his needs, whatever they be, right here, right now, in a way that feels good to both you *and* him. They involve a lot of closeness, connection, patience, and gentleness...both with yourself and with your baby. It is work...but you might find that the bond you create with your baby is worth the effort, worth laying next to him for an hour, worth giving co-sleeping a try, worth every ounce of breastmilk he drinks in the middle of the night, worth evey minute of love that you share together.
My suggestion is put away the books, turn off your brain, clear your mind of everything you have 'heard' or read.
Trust your instincts, honor your mother-wisdom, and follow your heart. He will only be little once. This is his way of communicating...of letting you know that he needs something.
If you suspect allergies or other health issues, I suggest getting in touch with a good naturopath!
Blessings of love and light to you and your family!