Any advice for keeping it a secret?! It seems impossible at my job!

Hi everyone so I work at an equine hospital (nursing sick and injured horses) which means theatre, xray, bonescan etc and also dealing with isolation horses. All of which, as soon as I find out I'm pregnant I'm not allowed to do. In my contract it states I must tell my boss as soon as I find out I'm pregnant which I did and she reccomended I tell 2 other nurses so they can "save me" from places such as xray in case I get grabbed by someone who doesn't know about my situation. Anyway, the 2 nurses know however for the past week, I've found it soooo hard to not give it away when someone asks me if I can xray a horse, or go into theatre and I have to mumble and try and think of an excuse immediately.

There are other jobs I can do such as lameness work ups (trot horses up and down) and go into mri.. But when there are no cases of that sort on one day I find myself wandering around making it the perfect opportunity to be grabbed!

I'm only 4 weeks and 5 days and don't plan to announce in until I'm 12 weeks. This is going to be a hard 7 weeks!! Shall I just go with "if people find out, they find out, but I won't tell them unless I absolutely have to (eg if the nurses who know aren't around and I get pulled into xray?)

My boss never puts me on cases but unfortunately our job is very much" if you aren't busy you help someone else who is"