My 15 week old daughter 'Lilia' started being fussy with her feeds about 3 weeks ago, going from a good 30oz a day to an average of 20oz, it may just be coincidental but it happened around the same time as we tried to establish a 3 hour EASY routine.
We have persisted with the EASY routine and have now established a 4 hour routine, very hard work, I made my partner take 3 afternoons off work to help out in the early days, as we also needed to wean her off her dummy, as she never slept more than 20 mins with it.
I also thought it could be teething, so have introduced a teething ring at Activity time. Lilia also suffered from colic but it cleared up at around the 12 week mark, I weaned her off Colief after 3 days, as I noticed she started to be sick alot after feeds, as soon as I got her off the Colief the sickness eased. I had noticed that Lilia seemed a bit more windy recently, even though I haven't changed her formual from Aptamil 1, so I have been trying Dentinox Colic relief, which you put in the bottle, she does seem less windy and this morning took a 7oz feed in 20 mins, Hooray!!! I'm hoping it's not just a coincidence and will take better feeds over the rest of the day.
Lilia also feeds better in the morning, she gets more tired as the day goes on, and by tea-time struggles with her feeds. I have started introducing very low key activity from 3pm, as not to over stimulate her, I usually just feed and change her, read her some stories and if the weather is dry take her out into the garden for 10 mins or ler her look out of the window, this also helps with her late afternoon catnap, as she seems to settle better.
It's so stressfull, I can completely see where you're coming from, it's all trial and error I'm afraid, personaly I would resist from weaning before 17 weeks, as you could make things worse, if your babay has an immature digestive system.
Hope some of the suggestions work for you, and if you find any answers yourself, please share them.
Tracey (Sheffield UK)