Great to hear that you went to speak to someone, thumbs up
Drugs and alcohol can and do indeed cause psychosis (most of the people I supported on the wards were suffering with this). Certain individuals are more at risk than others. Since your family has a history of mental illness you're in the susceptible category.
I know it's scary, but after what we discussed yesterday, you would probably get a better level of support if you went down the inpatient route.
You'd be in a low stimulus environment so you can relax, the staff there could chat with you, get to know you and observe your behaviour (it's nothing intrusive, we just keep an eye out. We know what we're looking for), this info would then be passed from the psych nurses to your doctor. All this info would then go towards getting you the correct evaluation, medication and therapy etc. It would also mean you getting help quicker. The more info they have the better they can help you.
Bare these things in mind when deciding on the best course of action, but more importantly: do what fells right for you.
Stay safe, take care