Sakit sebelah kanan memang common during pregnancy, especially around your stage, but since it comes and goes, I'd suggest checking with your doctor just to be safe and get peace of mind, better to confirm it's just ligament stretching or normal growing pains rather than worry sendiri, kan? A few of my mum friends also had this during second trimester and doc said it's the round ligaments pulling as baby grows, but yours lagi better to get checked since you're first time mom.