Question about breastfeeding while pregnant

Okay, so I'm still breastfeeding my 13mth old and of course food feeding. Lately she has gotten a case of bad diarrhea! It's yellow and very runny. She's had it for a week! I've stopped giving her juice and even fruit. I've given her more solids and even give her pedialyte. I've just about changed her diet except for the breastfeeding and she still has it. Can my breastmilk be the culprit? Has any of you ladies gone through this or going through the same with your other children? Thanks for any tips or advice.