It's most likely implantation bleeding, which is normal and usually nothing to worry about. But you can always ask your doctor about it :)
I don't think it's miscarriage. Brown blood early in pregnancy is usually old blood... it's nothing to worry about unless you are cramping very bad and/or bleeding bright red. Just tell your doctor at next appointment.
I thought the same exact thing almost had a panic attack and every thing but its completely normal . Dont worry about it . Its might happen a couple more times like it happened to me 3 or 4 times . I would go pee and wip and there would be a little blood but none in my under wear . So if of happens again dont stress . But if it gets heavier and more frequent I would probably go to the er . 9 times out of 10 tho your completely fine .