Hi mommas! I’m in my 6th week!

I’m a full time substitute teacher and this is my first year teaching. I was so so so very excited to get this job and found out I was pregnant two weeks ago. I’m nervous to tell my principal because - I am the one who’s supposed to cover classes long term - I’m worried they will be in a lurch without me and it may not look good to know that I’ll have to go on maternity leave after spring break and be out the rest of the school year. I was planning to tell them at the end of the first trimester (13 weeks) when I start to show. Am I overthinking? I may be too anxious to think about this clear headed lol… what do y’all think?