Can One Person Have Multiple Mental Disorders?

I believe it is more common to have multiple mental diagnoses than it is uncommon.

Yes, many mental illnesses are comorbidities. Also people having to navigate social/emotional settings with undiagnosed, untreated, or unacknowledged mental illnesses can exacerbate them, or if your condition(s) are used against you in a traumatic way or you otherwise find yourself in traumatic situations you can develop trauma related disorders either as an extension of how you're treated because of your mental health or independently.

Yes; I have 9 that I know of

While it may be uncommon, it is totally possible! Don't let anyone invalidate your experiences by telling you otherwise

Yes I've been diagnosed with severe anxiety and depression, bipolar, schizophrenic, paranoia, bpd, manic episodes linked with behavior, identity issues among peers and family, OCD (if that qualifies? I don't know) and multiple personality disorder