Loose stool & rolling over

I'm a FTM & My daughter is 15 weeks old exactly today. She hasn't rolled over yet. She is an exclusively breastfed baby and she poops every 4-7 days. Today she pooped and it was really loose and I felt a bit mucousy. It also looked like it had some curd like milk bits in it. She's never had diarrhoea before. What could it be? I had natural ice cream yesterday & the day before for the first time since pregnancy. Could that be the cause? My friends told me that kids do hv loose stools sometimes just before they roll over or sit up or some such milestone... is that true? Pls share ur experiences of that if that's the case...