I wouldn't say I have been in contact with a spirit before or not.. but when I was little I have seen silhouettes or shadows of humans that i couldn't see there. my ability started to go away until now at halfway through puberty, that i am seeing shadows out of the corner of my eyes. And there isn't a single person that I could physically see that would even made it possible or myself to make sense of it.
Do you believe you have a gift? Have you tried to communicate, does it scare you?? It could be that you simply live in a haunted location. If you are a medium you would see these things, and feel them all around you, everywhere you go you would have a sense of something being there.
Do you know how to cleanse and smudge, then seal your home?
Personally, I believe that the majority of spirits who take the form of shadows or silhouettes are those that do not have enough energy to manifest completely.
So, in my opinion, you have been in contact with the spirit world.
As you are able to see the shadows, it shows that you have potential in deeper skills involving mediumship. If you would like to, you could work to develop your skills and could become more in tune with the spirit world.
I don't know if they are exactly the same. But I see people and moving shadows out of the corners of my eyes too. (I also see elemental spirits can you?) I am always thought they were just spirits who want you to know they are there but are not ready for you to see them yet. A lot of the time when people see spirits it's not straight on anyways. It's figured in the corner of your eyes. If you can keep from panicking you should try to focus on them more. Learn to see what you can not see I guess.
Sprits and Shadows are akin. When ever I have worked with, banished, or summoned spirits I have seen them as shadowy masses, darkness's inside the dark. After all they are beings of the night. I would say you have mad contact with a spirit and that you should learn as much as you can about the spirit.