Without a little more context I can't be sure which of two interpretations to put on it: one positive, one negative, both slang (and not-quite-correct grammar.)
Positive: I had someone, and s/he had me; I was had. To have someone, in an indefinite sentence like this, means to be involved romantically with someone. "I once had a girl - or should I say, she once had me?" ("Was had" is not only grammatically nonstandard, but extremely unusual.)
Negative: I had had someone - or had I been had? To be had is to get fooled or cheated; in this interpretation the writer knows that s/he has just engaged in a battle of wits, and either won or lost... but isn't sure which.
Edit: with a bit more context (the passage is from a Dexter novel, TWELVE), the meaning becomes clearer.
Deborah has just been stabbed, and will perhaps be brain-damaged; Dexter has called an occasional boyfriend of hers. "Maybe he (the boyfriend) would help me with Deborah... It's good to have someone." It's good to have someone to take care of you.
"That reminded me that I had someone" - Dexter has a
girlfriend wife, Rita, to take care of him - "or perhaps I was had." Maybe it's the other way around - maybe Rita has Dexter to take care of her.