Ahhh mama, at 15 weeks ang belly mo dapat parang maliit na lump lang or kung feeling mo talaga parang preggy ka na, yan's totally normal, every body shows differently, kaya don't stress! A few of us moms noticed na some showed at 12 weeks, iba naman ay 18-20 weeks pa bago obvious, so wala talagang standard. Best talaga na i-check with your OB para ma-confirm na lahat's on track with baby, at sila na ang makakasabi kung paano ang weight gain mo relative sa baby's development, they'll have your baseline kasi. How are you feeling otherwise?