Sayang, pain on one side especially kalau teruk like this kena jumpa doctor or pergi clinic/hospital jangan delay ya, even if feels like gastrik, better safe than sorry masa pregnant first time. Could be many things but doctor perlu check properly untuk peace of mind you. Meanwhile rest, jangan stress sangat, and minum air banyak-banyak. A few of my mum friends rasa macam-macam weird pains early pregnancy but still, jangan ambil risk, get it checked out today okay? Take care!