Could I be pregnant if I had sex two days after ovulation?

If you knew that you'd definitely already ovulated, then taking Plan B would be pointless, as it works by delaying ovulation. It can't do anything, & you wouldn't become pregnant if you'd already ovulated, anyway.

If you were relying on an app/website to tell you when you ovulated, rather than charting your body's signs each day, then they are just a rough guide.
In that case, you could have been ovulating, & Plan B would be useless. It can't delay what's already happening.

In that situation, you'd need the other emergency contraceptive pill, called Ulipristal Acetate (Ella). Either that, or to have had an IUD fitted by a doctor. Either of those things could be done within 5 days/120 hours of the unprotected sex.

You can become pregnant from the pre-cum (fluid that he leaks when he becomes turned on), even if he did not ejaculate/cum inside of you.

You may both want to be checked out for STDs, as you can carry those without symptoms, & some of them you can carry whilst still being a virgin.