Can I be pregnant if I took birth control pills after ?

I take my birth control pills once every three days instead of daily, so that I get my period less frequently. (ie: one period every 3 months instead of once a month). But now I think I may be pregnant. I don't have regular periods, so I don't know when I can take a pregnancy test because they say: wait X days after your first missed period. My question is, if I took a birth control pill the day after I had , can I be pregnant? Does my birth control regimen make it less likely for me to be pregnant?