I'm Never Later On My Period, At Least Not By

I'm never later on my period, at least not by more than 1 or 2 days, now... I'm 10 days late and I'm not hoping for another baby as I have a two years old. I haven't done any tests to confirm pregnancy but m certain I am coz m late. I don't want to go for surgical termination. I opt for pills instead. Which ones are the best? And can I get them over the counter?