Hai, normal lang sis! At 18 weeks the hormones are already working overtime, plus your body is working hard to support baby, so rasa super tired is very much part of the journey. A few of us mums felt exactly the same around that time, macam mata je nak tutup je bila baring. Just make sure you're eating enough, staying hydrated, dan getting proper rest lah, tapi if the tiredness is extreme or you're having other symptoms yang worry you, best check with your gynae just to be safe, okay?