Oo, normal yan, mama! A few of us na malapit na manganak noticed the same thing, loose stools or frequent pooping can actually be a sign na approaching na ang labor dahil sa hormonal changes at how baby's dropping. The dark/itim na tae is usually just from iron supplements, pero since you're 38 weeks na, better to mention it sa OB mo just to be sure everything's good, lalo na if may other signs ka like cramping or spotting. Wishing you a smooth delivery soon!