My Fiancee Is Changing, I Am Worring So Much

My name is Hassan, i loved my girlfriend for 8 years, then we got engaged and we were so happy ... Since 2 months she is changing, just i dunno what`s happening, my mind is getting crazy... Actully i love her so much, more than my life, more than world, more than anything ... As well she loved me this way .. But i dunno what`s getting wrong with her... I am worring so much, please help me, this is very important, she is my life, if something happened i`ll die !!!!