Ay, second trimester is when tayo usually nakikita na talaga ang weight gain, kaya I'd honestly suggest bringing this up sa OB mo sa next check-up para sure lang, better safe than sorry talaga, especially since baby needs the nutrients to grow properly. One of my mum friends had something similar and it turned out she needed adjustments sa diet, pero it really depends sa individual pa, so best to get it checked. Kahit minimal weight gain lang ay possible, gusto lang nating ma-monitor na baby is developing okay through the ultrasound at baby's measurements!