Earliest time for a pregnancy test?

Lena • happily married Yogi, Blogger, Artist...misssfaith.com
I'm wondering how soon after one conceived a pregnancy test would show a positive result (even if it's a faint line)? 
After my MC the test now is complete negative and I was wondering if I would conceive now, when would it makes sense to test again? I haven't had an AF yet, so my cycle isn't back to normal.