I'm just going to address the first sentence.
Firstly, it would sound more natural to say a few days ago rather than a few days earlier when you're talking about time before the present. When you're telling a story about the past and you have to mention something that happened before that point in the past, then you have to use "earlier" instead.
Secondly, the content of the sentence doesn't make sense as an answer to the question "What are you up to?" It's not a yes-or-no question, so you can't just say "I am" or "I was"; you have to specify what you were up to (even if you were just up to "something.") So either of these could work:
"What are you up to these days?"
"Nothing. Though I was up to something a few days ago..."
"Are you up to anything these days?"
"No. Though I was a few days ago..."