Blundered on is not really a good expression, you would most likely say 'I Babbled on' or 'I Rambled On', A lot of the time you may hear 'waffled on' or something like that, its a more casual way though.

We (english speakers) do not normally use this expression, but in the context you stated it would be more like stumble through a conversation without really grasping the concept the other person was saying or your speech was totally confusing.