import re
text = "1. Notice \nSome text \nEnd Notice\n2. Blabla \nSome other text \nEven more text\n3. Notice \nSome more text\nEnd Notice"
pattern = r"^\d+\. Blabla.*(?:\n(?!\d+\.).*)*"
result = re.findall(pattern, text, re.M)
print(result)
aW1wb3J0IHJlCnRleHQgPSAiMS4gTm90aWNlIFxuU29tZSB0ZXh0IFxuRW5kIE5vdGljZVxuMi4gQmxhYmxhIFxuU29tZSBvdGhlciB0ZXh0IFxuRXZlbiBtb3JlIHRleHRcbjMuIE5vdGljZSBcblNvbWUgbW9yZSB0ZXh0XG5FbmQgTm90aWNlIgpwYXR0ZXJuID0gciJeXGQrXC4gQmxhYmxhLiooPzpcbig/IVxkK1wuKS4qKSoiCnJlc3VsdCA9IHJlLmZpbmRhbGwocGF0dGVybiwgdGV4dCwgcmUuTSkgCnByaW50KHJlc3VsdCk=