Black Dogs Options

Forgive me if this is the wrong forum to post this in, but I haven’t seen anything about it yet.
Throughout my childhood I often saw a large black dog following me or walking around my yard at night. It would come and go but was mainly present during times of high stress. Anytime I asked anyone I was with about it they told me they didn’t see anything and thought I was just imagining things.
I’ve tried looking it up online and collected a few folktales about them but most seem to imply that it is a death omen of sorts. Given that I’m a live after twenty some odd years of seeing it I rather think the folktales are off a bit but I’m unsure as to why its there and what if anything I should be doing about it.
It has shown up in a few pictures I’ve taken during rituals, even though no one saw it at the time. I thought it might be some sort of familiar except that it always feels vaguely threatening. Anyone have a similar experience or advice?

I had similar 'waking dream' experiences when I was a boy, except with me it was buffalo. I have had periods in my adult life in which I have had very real dreams about buffalo. They were huge and scared the hell out of me for some reason. I discussed this over coffee with a shaman friend of mine during one of these periods. He said that I should be cauutious, but try to talk to it or listen to the message. I did so and haven't been visited since.
In my case, it wasn't a power animal, but I agree that it could very well be in this case. Look at yourself and see if you have any canine qualities or energy.