If you have dedicated yourself, you have one, if you did not, 99% that you don't have one.
You can find tricks how you can find your guardian, here in the forums.
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If you aren't a Blood dedicated SS, you won't be able to connect to a Guardian. Even if you have a past life connection to one, they will first guide you to dedicate before any further communication is made.
I had connected with my Guardian before I found the Joy of Satan, and she guided me to the Joy of Satan, then she guided me to dedicate, after which I could re-establish my connection and relation with her.
Serbon asked if you are dedicated, since that is the pre-requisite to work with the Gods and connect with your Guardian Demon.