Fussy gy screaming newborn?

i have a 3 week old and the past couple of days she is really fussy, VERY gy, ping green runny stools, and hysterically crying. i am feeding her my milk during the day (i pump) and feeding her parents choice organic formula at night to supplement. her father is lactose intolerant which developed at a later age for him. we give her gas drops but i am wondering should i switch to another formula? should i consider colic? I don't think it is what i am eating besides maybe a packet or two of splenda during the day with some foods. any suggestions would really help!!! she is gaining weight and eats normally (2-4 oz).