Aw mama, yan ay pretty common sa second trimester actually, ang ligaments mo lumalaki at nag-eextend na para sa baby, kaya may clicking or popping sounds talaga sa joints, especially pag tumataas ka o nagbabago ng posisyon, and sometimes may slight sharp feeling din! A few of us here sa mommy group din naramdaman yan around 15-16 weeks and it went away after a few weeks. But since you're worried and this is your first time, better check with your OB lang just to make sure everything's good, they can give you peace of mind at ma-rule out kung may iba pang thing, plus mag-advise ng proper positions para mas comfortable ka. Take care, mama!