He is not ready for solids= he is getting constipated. That is the signal that his body is still developing and not ready for solids.
For the 1st year of life.... breastmilk is a baby's PRIMARY source of nutrition. Not solids. In fact, solids is not as nutritionally dense, as breastmilk.
A baby needs to feed/nurse on demand. Yes it is hard. Yes it takes most of the day. And it means doing it at night too.
The baby is growing.
Feeding or sleeping according to a "schedule" is not good. Because, a baby's appetite and growth-spurts, cannot be predicted, and it will not be, the same every day or every night. It changes all the time.
Hence, nursing on-demand is the healthiest way to feed a baby.
And, babies also do what is called "cluster feeding." In which they nurse every single hour. And this is normal. It reflects, their biological needs.
Both my kids had GINORMOUS appetites and I nursed them exclusively on-demand, day and night, for the 1st year. Yes it is not easy. But I did it. And they are healthy and grew like weeds.
My kids as babies, nursed... every 2 hours, sometimes less, and this was day and night, even though I had tons of breastmilk. They drank my dry, each time, and I used BOTH breasts per each nursing session.
Babies wake at night.
They also go through many developmental changes and teething and growth-spurts. It is not easy for them, either.
And, a baby's sleep patterns, ALSO changes all the time. It is never, static or the same all the time.
Their organs/brains/coordination/cognition is developing.
When/if a baby is over-tired as well, or over-stimulated... it makes it MUCH harder for a baby to sleep or to fall asleep or to stay asleep.
In other words, sleep begets sleep.
If your baby is hungry all the time, nurse him.
Also make sure that you are producing enough milk?
And that, he is latching on, properly.
If you are not producing enough milk or if he is not latching on properly, then a baby will not get enough intake.
There were MANY times, that my Husband would see me nursing my baby when he went to work in the morning. Then when he came home in the evening, there I was breastfeeding again. To him... I was nursing ALL ALL ALL day! And he'd ask me if that is what I do all day. And I would reply: 'YES, this is what I do all day. Your kids are babies. This is what they do. But they are healthy and developing well." Then he was proud of me. He knew it wasn't easy.
Contrary to popular belief.... solids does not make a baby sleep longer or better. It is not the answer. In fact, for many babies, solids actually makes more problems for the baby, if their body is not ready for it.