Aiyoh, 3 hari tanpa poo memang bikin worried kan, tapi dengan mixed feeding, sometimes babies can go longer especially if digestion slow sikit. Cycling exercises and tummy massage you're doing tu dah good, but since dia baru 3 bulan and first time macam ni, better check with your paediatrician just to be safe lah, especially to rule out any feeding issues or if dia needs water in between feeds (some doctors okay, some tak). A few of my mum friends punya babies like this after switching or mixing formula brands, jadi sometimes boleh juga kena try different formula atau feeding schedule. Trust your gut, if you rasa ada something off, don't wait, go see the doctor je, better peace of mind!