I really feel you on this, those first few weeks with a gassy baby can be so exhausting and heartbreaking to watch. What helped my little one was doing gentle tummy massages in a clockwise direction and bicycle leg movements after feeds. Make sure to burp baby well mid-feed and after, not just at the end, as that made a big difference for us. Since your baby is only 3 weeks old, it might be good to bring him to see the PD just to be safe, so they can rule out anything else and advise you properly for such a young newborn.