That doesn't sound like implantation bleeding. You're right, typically with implantation bleeding there wouldn't be any clots and it wouldn't last more than a day or two, though I know we've all read anecdotal stories where women have what seems like a normal period only to find out they're pregnant, so it was wise to take the tests anyway. If you took the tests at least two days after the bleeding stopped then I would trust them.
Sometimes, periods are just wonky and different from past periods. If you continue to have lighter-than-normal periods, it's not a bad idea to bring that up with your doctor just to make sure it's not a sign of a treatable hormone or thyroid condition.
As for a lessened appetite and sleep issues, these could be related to hormones (ugh, we're always at some weird point in our cycle aren't we?), illness, or even anxiety. If they continue for more than two weeks and have a profound effect on your day-to-day functioning, let your doctor know.