Sakit ari-ari memang normal masa pregnant, especially bila banyak gerak atau dalam certain positions, tapi at 5 months kena check dengan doctor just to be safe, bisa jadi growing pains je, tapi better to rule out anything else. A few of my mum friends ada kena sama, and after see the gynae, most were fine lang, just kena adjust position tidur and take it easy. In the meantime, try to rest more, avoid heavy lifting, dan pakai maternity pillow para support better, memang life-changer! But do follow up with your doctor soon ya, just untuk peace of mind.