Really annoyed at people finding out

I'm 7+2 today and 2 days ago someone congratulated me on my pregnancy. This person isn't someone I've told and they're going on pure rumour. My work is dreadful for gossiping and I know people are wondering if I'm pregnant etc. Anyway I was totally shocked and asked how she knew to which she said she "guessed". Lies! Anyway I'm trying to get over it but im just so furious that someone else knows that I don't want to know. This person, who I used to work with, doesn't even work in the same area as me anymore. I still can't believe she actually congratulated me knowing fine well it's not yet public knowledge. Acht there's nothing I can do about it just now, trying to not dwell on it but I keep thinking about it every so often. Now I'm worried that she's confirmed to the person starting the rumours that she was right, because everyone will know very soon if that's the case. I wish I could just stay off work till 12 weeks!!!