Aik, normal je lagi la at 4 months, some babies ambil masa sikit lebih untuk head control, especially kalau premie or just naturally slower in that milestone. A few of my mum friends' babies baru strong head control around 5-6 months, so don't worry sangat. Tummy time yang banyak helps a lot, even 10-15 minutes few times a day boleh strengthen neck muscles dia. Tapi kalau you're worried, better check with your paed at the next visit, they'll assess properly and boleh guide you if ada anything to work on. Keep doing tummy time and enjoy the cuddles, most babies catch up just fine!