I have this girlfriend that I have dated for almost 5 months. She says the only thing that will make her happy is stay the night. My questions are- Why does she want me to stay the night so badly? How do I tell her I don't feel comfortable doing so? What do I do if she says I guess then it won't work out if you don't stay the night? Any help will be gladly appricated

You need to be honest wit her, explain you issues and that your not ready, if she truly likes you she will stick with you through thick and thin. 5 months is not really very long, your still getting to know each other and building up trust. But honesty is the best policy. If she doesn't understand perhaps you need to think is she worth it?