Ortho try-cyclen Lo nauseas. please help!

Betzy
I started ortho try-cyclen Lo on Monday, im on my 3th pill today and I feel really nauseas. I haven't really ate in the last 2 days because every time I do I feel like throwing up. 
 
My partner and I recently had sex after I got my iud out about 2 weeks ago. Unprotected but he did Pull out. On Monday at the clinic they took a pee sample and they told me I wasn't pregnant. I'm thinking of getting off the pill on Friday just because I want see if my symptoms change or not. What are the posibility of me becoming pregnant if I stop taking OTCL or missing a pill ?