Aah, formula change memang sering cause constipation macam ni! A few of my mum friends pun experience the same when they switched brands, some babies' tummies just prefer one formula over another. Since baby's perut lembut je, no bloating, and dia passing gas, mungkin dia just adjusting pa sa new formula, but 3 hari tak berak is worth checking with your pediatrician to make sure everything's okay and maybe discuss switching back or trying a different brand. In the meantime, boleh try slow-introduce the new formula mixed with the old one over a few days instead of straight switch, or ask the doctor if you should go back to Frisolac while adjusting gradually.