i didnt have any until week 5 of my pregnancy. but its not uncommon. the only way it might be an early mc is if its heavy bleeding and its painful too. the only way to know if its IB or just mid cycle spotting is to test in a few days and see if its positive. gl!
also, when i had it, it lasted only two or three hours tops and it happened twice but a few days apart. the spotting was big spots of beige. no pink or red or dark brown. just super light brown in my experience. but it can be pink or brown and everything be fine, too.