Hello, not read any other posts, may post again later.
All babies follow their own pattern, for term babies it's fairly close, but for premature babies it can be massively different. Some will be like Tink and do everything as though they were a term baby, some will do what they should have been doing if it wasn't for that little hiccup where they were born and some will do something in between.
That said 17 weeks or 23 weeks is probably a little too early really. There has been a study that has shown premature babies stomachs take longer to mature, even with CGA, than term babies so the longer you can hold off the better.
At around 17 weeks babies will go through a growth spurt and it sounds like this is what you are going through at the moment. At a growth spurt babies will guzzle and guzzle, day and night (but especially at night because that's when mum makes the best milk) to a. tank up for the growth spurt and b. make sure mum is able to cope with the big baby that she is about to have. It's also possible with the chewing that a tooth is due, I noticed that she was teething at 3 months (from birth) and she didn't have a tooth until she was 7 months.
Before a year food is for fun and experience, there is a little nutrition to be gained from it but not as much, especially calories, as in milk. If you think about your own diets, you give up full fat milk, not carrots. The same works in reverse. If your baby is hungry then give it the full fat stuff!
Right, Tink was a 31 weeker and we waited until 6 months actual age, although I wish I had waited longer she actually did really well, she was BLW so she wasn't pushed past what she could do. I think that BLW is the best way to gauge when a baby is ready, if they can't do it they're not ready.