Just got hired for a new job but found out Im pregnant

This is going to sound far fetched but I just found out Im 18 weeks 4 days pregnant 🤦I have a 2 year old but I developed a gastrointestinal disorder since having him so I didn't think anything of all the symptoms. I literally just got hired 3 days ago as a waitress and I feel like if I tell them they'll think I was hiding it from them to get the job or something. How do I tell them without losing my job? 😅 I really need the money now more than I knew