Nausea

My period ended a week ago. My SO and I rely mostly on the pull out method since I am taking the pill (and have been for months) and over Valentine's Day weekend we think he might have messed up. It's been a week since then and for the past few days I've been feeling unusually nauseous, especially today. I'm leery about eating in case I get sick. 
If I was pregnant would the nausea appear this early or are we just overthinking things and I'm just not feeling well?