It's something on Apple's side. Why not just have them set you as an SMS-only contact since you don't have an iPhone and it seems to resolve the issue? It's possible that somehow someone was able to spoof your number to associate it with Messages but trying to track that down and get it resolved may be a full-time job for a few days.
Our friends over at
http://imore.com might be able to provide some insight into what's happening as they deal with Apple stuff more often.
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