It doesn't have any meaning, but mike was saying it has meaning.
It has a few potential meanings. It does not have a meaning that can be defined without context. Mike gave one thing that it could mean, but if your phrase appeared in a different context, such as the one I gave you, it would mean a completely different thing - and Mike would be wrong. In fact, if you read Mike's post again, he gave you the meaning for "overly conscious" which was not your phrase. He apparently read your phrase as an error for "overly conscious" or "over-conscious", which it might or might not have been.
Please explain the meaning of this sentence "I was being over conscious while doing the work"?
That is a sentence which has the meaning Mike suggested, and which would have been useful to include in your first post.
But perhaps you mean 'overly conscientious', because "over[ly] conscious" doesn't really work.