What are the chances I’m pregnant if I took Plan B the night before supposed ovulation?

It's impossible to know, unfortunately. No one knows how long it takes for the drug to act, even if you were not already ovulating.

To add to that, ovulation timing can vary from woman to woman. It's not always day 14 every month. The only way to know is to chart your fertility symptoms each day, in advance, or to use an ovulation test.

If you are in the situation where you're that close to ovulation, again, I'd recommend using the other emergency contraceptive pill, called, Ella (Ulipristal Acetate), if it's available in your Country. It's the only pill that's proven can prevent pregnancy during the 24 hours around ovulation, itself, although, even that pill is not guaranteed.

The discharge is very likely caused by Plan B, but it doesn't tell us whether or not it worked to prevent pregnancy.

I'm very sorry that I can't give you a definite answer.

You may find you period is late. Some women can wait months for a period after using Plan B. More typically, if there is a delay, it's just a week or two. If it is longer than a week, your doctor may agree to do a blood pregnancy test, to put your mind at rest, whilst you are waiting.