Formula issues - please help!

Okay so a little back story. Baby girl is 3 months old, she suffers from colic. We used to give her aptamil milk. Her colic was very bad and she was very constipated so we changed to aptamil comfort (for colic and constipation. Less lactose and very thin formula) she was fine on it although was still constipated some times only did a poo once every couple of days and the consistency and smell was awful! As was the smell of her farts lol.

Soo, about a week or so ago she became very fussy with her milk all of a sudden. Would just completely refuse it till it got to the point where she wasnt getting enough milk in a day. She did this for around 4/5 days. So as her colic symptoms have been getting better over time, i decided to switch up her formula and give her cow and gate. I originally got the ready made bottles as didnt want to waste a whole box of formula incase she didnt take to it. She took to it amazing! So i was staying at my mums and mum went and got around 10 of these bottles and its what i fed her the whole time i was there. She even started drinking 2/3 ounces more each feed than she was before. Started putting weight on and generally seemed happier. Soo i went and brought the cow and gate box. Now since making these myself, she has become very gassy again! I think the problem is the froth at the top of the bottle when i make up the formula. So much froth! So many air bubbles! Its realy affecting her, shes not sleeping well, she cries out in pain. Grunts for ages and finally lets out a fart, is really irritable in the day aswell and her stomach makes lots of noises! Iv tried burping her regularly, gripe water, i also give her infacol before feeds and tried to shake the bottle when making the feed slower in order to minimise the amount of froth but no luck! I cant afford to give ready made bottles to her full time as it works out so mch more expensive! Any advice ladies?

Sorry for the long post!