Some lady support would be nice

Okay, so where to start ill just say that some lady support would be much appreciated as im not sure if im to feel this way.

Okay, So about a month a half ago my 15yrs old (yes I know so young but im not the parent as I tried my older sisterly talk) sister spent the night with a boy ( I was pissed when I found out) they of course had unprotected sex!!! Well I made her take a couple test about 3 weeks afterwards all negative. So here we are 10/27 and she missed her Fing period. Shes irregular sometimes, but I did my older sisterly talk again. Tonight she told me that she had her physical at school today and the nurse said her stomach felt different! The nurse asked my sister if she missed a period and or does it hurt? My sister said im irregular and no it doesnt hurt. Now i called our "mother" to fill her in and pretty much didnt have that much of a reaction. But the point im getting at is either one she pregnant or two a serious health issue that I cant do nothing about due to not being the parent. Also if she turns out to be pregnant I am already an emotional reck due to thats my baby sister/daughter(raised her pretty much) im suppose to protect her shes a baby having a baby. Im 26 and my husband 27 have been for 3 years ttc. And im almost done with my ttw and neg test till and my baby sister might be pregnant at 15. Im so heart broken but yet I see haterd towards her. Am I wrong for feeling that way? Sorry its long thanks ladies in advance.