mental health, think I'm hearing voices?

Georgia
So I have always struggled with depression since around 11 years old, I haven't ever seen a psychiatrist just multiple GP's (doctors) who have always put me on different meds etc, recently I started mirtazipine and all went well until a few days in, My anxiety was through the roof and I felt like I was experiencing a manic epidsode, then inside my head all I could hear was an unusual voice talking incoherently. This freaked me out so much I've completely stopped my med and I'm waiting for a follow up appointment from my GP. 
I think I've always heard 'voices', but it's always random things like "caution" or complete nonsense that I can't make sense of. I want to speak to my doctor but I'm worried they won't take me seriously and that it's just a symptom of an anxiety attack? Although sometimes the 'voices' are completely random when I'm doing day today things.