I used to have hallucinations. Like, when I was sitting on a train once I "saw" my attackers get on and sit in the seats all around me, that kind of thing.
I've also had problems in the past with hallucinations from hypnopompic/hypnogogic states, which is when you're in a consciousness inbetween sleep and waking. Many people experience someone coming into the room, walking over to them and pressing down on their chest (in the past it was called hag-riding, or being ridden by a witch). I didn't used to get that, I used to get other horrors.
Not speaking scientifically but from how I experience things, I group hallucinations together with flashbacks and nightmares. I started doing visualisations to protect myself from all three, and don't have them any more.
I haven't experienced delusions, unless you count obsessive compulsive disorder things, like being convinced I've unlocked a window and left it wide open after I checked it.
Do you see delusions and hallucinations as being connected, or part of the same thing? I see delusions as being about thinking/ruminating, and hallucinations as being about feeling/experiencing.