the pencil tool wont stay the same width when im using it either it keeps
switching to no weight and is invisible after changing it to my desired
look.
Have you set up the setting in the Appearance panel ? Turned off "New art has basic appearance"?
That's important.
Also: What exactly do you want the artwork to look like?
And then: In Illustrator a stroke or a brush are attributes of a path. They can be applied and changed later on.
But: the brush tool saves everything you do with your stylus into the path. This only makes sense with a brush. Only then you can also see it. That's just how the tool works. You don't like how the tool works? Make a feature request. Feature Request/Bug Report Form
But until then it's how the tool works and you will have to use the pencil tool if you want to draw with a plain stroke.