Haih, I understand betul lah worry ni, a few of us mums dengan toddlers yang lasak camni memang ada jugak, especially around that stage when they're so unpredictable! The good news is at 18 weeks, baby mu sudah protected quite well by the amniotic fluid and uterus itself, so sudden jabs and tumbles dari toddler tu normally okay je (though I know scary feeling!). That said, since you're genuinely worried about the impact, worth a quick check-in with your doctor just to put your mind at ease, they can reassure you based on what they see. In the meantime, boleh lah try gently redirect when he does that, I usually distract dengan toys atau activities yang dia boleh main side-by-side without climbing on me, helps reduce the anxiety a bit!