I may be pregnant and just got a job at a spa, how do I get out of...

[volata_bionda]

...aromatherapy without telling her? So, my husband and I have been trying to have a baby within the last 2 weeks. It's too soon for the pregnancy tests to show up if I am pregnant yet or not. I got call back from a place I applied at a while ago for a job as an esthetician at a spa.
I went in for the interview today, and got the job!! But I don't want to tell her I'm pregnant yet 'cause I don't know for sure yet if I really am. And I wasn't going to say anything until the 2nd trimester anyways since problems can happen during the first trimester (if I find out I am pregnant).
I don't want to lie to my new employer, but I don't want to lose my job either since I just got the job and technically haven't started it yet.
So, my problem is....tomorrow I am going in so she can do a facial on me....within the facial, steam towels with aromatherapy are used 3 separate times (her oil mixture has several things in it and I don't remember anything she listed off, and she actually couldn't remember everything in it either...).
She only uses like three squirts on each towel so I don't know if that will make a difference.
I just don't know what I should say tomorrow, should I say I may be pregnant and possibly be denied the job and cause her to regret hiring me? (keep in mind I have yet to sign any papers, she just told me verbally after the interview). Or should I make up an excuse that I am claustrophobic? (I can't say I'm allergic to anything since I handled the towels today with my hands and am fine....).

I need help! What would you do if you hired someone and then found out they were, or may be, pregnant shortly after?? DO you have ideas on how I get out of the steam towel?? I don't want to have a miscarriage or birth defects if I am pregnant
a lot of escentual oils used in aromatherapy that are on steam towels, cause miscarriage and/or birth defects