Urgent-CowMilk or Formula. Cow's milk?

Hi doc, My daughter is 2 mnths and 5days old (normal delivery) and I have been breastfeeding her and plan to exclusively breastfeed till I introduce some solid food .But today I noticed that she has been feeding for every 15 mins and when I tried to express little milk I was not producing milk ,and so found my milk supply has fallen too much that she is not getting enough milk so I am forced the thought of intro addition source of milk for her and thought of giving Cow's milk but,  when I searched about this I read many articles saying formula is better than cow's milk ,So which is preferable cow's milk or formula (eg. Lactogen) ? If formula milk then any suggestions which is better for her -lactogen or any other formula ?? And how to introduce her to formula or cow's milk? Also help me on food items I can have to increase my milk supply as early as possible withoutProducingGasFor her.Am on strict diet with no spicy foods allowed. Also she is too gassy So pls suggest which is best .