Then sleep in busy truck stops. They may be noisy with trucks coming and going all night and sitting there running, but at least there are people around, and washrooms handy. They have restaurants and often they have showers. I would suggest, however, that driving very much in the dark on unfamiliar highways with minimal sleep is not a safe thing to do. Get a good night's sleep in a comfortable place and do your driving well-rested in the daytime.If you feel sleepy in the daytime, catch a few winks at a highway rest stop.
Studies have shown that people who drive while tired are the same safety risk as people who drive drunk, and you wouldn't do that, would you? At 19, you are a relatively inexperienced driver and it doesn't sound like you've done any long road trips so far. Getting there fast is great; getting there at all and uninjured is even better.