Less gain weight

Hi mommies! Help naman for baby.. findings kasi ng doctor may UTI sya, anitibiotic sya now.. pero poor gain weight sya. 6.3kg lng sya - mag 5months na sya sa may3. Any mommies with same kg. Dpt ko ba ikaworry? Wala advice doc sa weight e, sabi lang kulang sya 1kg, then hindi nya dinidede yung tsupon, sa boob ko lng tlga sya.. and hindi nakaka dede maayos kasi distractive pg May sounds. Any same situation? Any advice..