Aiiii I feel your pain, mama! My eldest was underweight jugak dulu and kena ambil darah, memang heart-breaking tengok anak kecil kena cucuk. Honestly, buat dia diam completely susah, but what helped was I buat dia relaks dulu dengan cakap pasal reward after (ice cream or favourite snack), let the nurse know dia nervous so they can be gentle, and I hold his hand and cakap nonsense jokes the whole time so he focus on laughing instead of the needle. Some kids memang kuat bergerak, so maybe coordinate dengan clinic nak 2-3 people to help keep arm steady kalau perlu. The best part, it's over in seconds, and you're doing the right thing by checking his health. Cheer up, you're a good mama!