Oo, totoo na usually mas matagal ang labor sa first time moms, marami sa mga kaibigan ko na panganay talaga umabot ng 12-14 hours pa lang, kaya huwag mag-alala, that's normal! As for hindi mapapansin ang labor, it's rare but possible especially sa early stages, some moms don't realize pa kung talagang contractions na or Braxton Hicks lang kaya important talagang malaman mo ang difference (regular at nagiging mas malapit ang interval vs. random). Since you're already having pelvic and back pain at 37 weeks, honestly best to follow up with your OB agad para sure everything's on track, kasi alam mo naman ang peace of mind na kailangan natin ngayon!