Sakit bawah perut masa pregnant memang common, tapi at 23 weeks kena perhatikan jenis sakitnya, if it's more like stretching or heaviness terutama when you walk or stand, usually okay je, tapi kalau sharp, persistent, or followed by bleeding, you should definitely check with your doctor cepat-cepat. A few of my mum friends had the same experience and it turned out to be ligament pain or just the weight, tapi better safe than sorry especially at this stage, your doctor can do a quick scan to make sure everything's fine dengan baby.