Sayang, this really needs proper medical follow-up, please jangan stress sangat dulu, okay? Your doctor is right to monitor this closely, because low beta hCG at 4 weeks could mean the dates are off, or it could be a concern, but only repeat blood tests in a few days will show the pattern (hCG should roughly double every 2-3 days if healthy). Some of my mum friends went through this exact worry and turned out fine, dating was just off, but some didn't, so you really do need to follow your doctor's advice for the repeat test rather than guess. Hang in there, and make sure you go for that follow-up blood work they're ordering. Sending you strength