Falling out of love?

My fiancé and I have been together for 4 years now and we got our marriage licens and we have you'll the end of May to get married well here the past few months I've been idk I don't really want to be around him he has been getting on my nieces and very irritating like I don't even want to have sex anymore I'm not happy like I used to be and I feel like I'm trapped he has not made any effort to take cake of our kids and I we have been living with his family the entire 4 years idk If I can take this anymore.. Am I falling out of love or am I letting my attitude get the best of me idk