Don't want to lose her... really need help

OK so I have been trying to think of a way to explain my problem without sounding like a man that's just trying to control his woman but the best way to explain this is just by using the best words I myself can thing of so while you read this if you can think of a better way this could be explained and take it that way plz..... Me and my fiance have been together for 3 years now and to me she is the most beautiful and amazing woman I have ever met in my life... I got into a little trouble that ended up causing me to spend a little time incarcerated. Before I went in we were just fine. But when I came home everything changed in a month. She started being mean and yelling all the time telling me what to do taking things out on me that isn't my fault. I feel like she is acting this way because I'm not in

Marry her or leave her. 3 years without marriage is too long for a precious lady.