First supplement?

Eveamlizya

So, we've had a lot of problems with DD the past month with her not being fully satisfied after feedings during the day...at night, she's really so sleepy she doesn't care if she's full.  She'll feed from both breasts and still gives hunger signs, but she isn't gassy or refluxy or anything like that.  Pedi said that we could try giving her about .5-1 oz after breastfeeding as a "desert" and see if that helps.  So, today, after trying and trying to keep putting her back on the breast (she just pulls off when I'm empty because there's nothing coming out so she gets mad), I pulled out a bottle and gave her a third of one of those 2 oz premixed enfamil bottles.  She took it great and drank the whole thing without a second thought and...no hunger signs afterwards.  She had one hell of a burp afterwards, but I expected that.  Not only did the hunger signs go away, but instead of her usual hungry every 1 1/2 - 2 hours...she lasted about 3 hours before wanting to eat again. 

My question is about her pooping, she isn't constipated or anything and I have noticed that it's definitely a darker color and a tiny bit thicker, but she'll cry for about 15 minutes before she poops which she never did before and I can hear her tummy rolling too.  Do you think it's just the first time with formula has messed her tummy up a little?