About my daughter: At 4 months she was 26" long and 15 lbs 6 oz. And wearing 6 to 9 months in clothing. She is 8 months, 22 lbs, and 29". She is not a fat baby very lean in fact she is just very LONG. She wears 12 - 24 months in clothing.
My little one did the same thing. At 4 months I was feeding her 4 oz at 10 pm, 12 am, 2 am, 4 am & 6 am, etc. Every 2 - 3 hours. I was a stay at home mom so I could catch up on my sleep during her nap times. She is a very long baby and I figured she just needed to eat that often. At her 6 month check up she was still eating every 3 hours and her doctor was concerened and said she should be sleeping through the night now and just to let her cry. Well...as a mom I just couldnt do that because she was hungry at those times. I never picked her up I would just give her a bottle and she would go back to sleep. At that time she was on 5 oz.
She started day care at 6 1/2 months old and that did make a difference! She was tired earlier and slept longer. She on her own from the time she was 4 months to now at 8 months she would constantly change her schedule. She would go to bed earlier and would cut a feeding out on her own with nothing to do with me or what I did.
Now at 8 months she eats 6 oz and when she comes home from school at 5 pm is feed her dinner (stage 2 food with 2 tbs of cereal) then her bath, she then gets to play until she is tired which is around 5:30 to 6:00 and then she is placed in bed with her blankie and fed her bottle. I wake her up at 11 pm change her diaper and feed her a bottle and she is asleep until I wake her up at 6 am. I learned to feed her more before bed (8 oz) which made her sleep longer.
The one thing I did learn is I would let her cry for a few min to let her get tired out on her own before feeding a bottle so when I did feed her she would fall asleep. It also turned out that she liked to put her blankie over her head and this gave her a comfort.
Babies schedules change all the time once you think you have a routine they will change it on you. Every baby is different what works for one baby isnt going to work on every baby. They are individuals with individual needs.
There is hope one day she will become more scheduled on her own I assure you. It will just take time and patients!!!! Lots and Lots of patients! I am married and my husband works nights and I did this all on my own 24/7...so I feel your pain!
Good Luck!!!!!