Can The Bleeding Be A Result Of The Morning-after Pill, And Should We Be Concerned About Pregnancy?

My gf took morning after pill on 5th May, 20h after risky unprotected intercourse. Her 1st day of her last period was on 28th April. On 12th May when its hers ovulation day, she feel like its her period and got heavier bleeding then usual, it lasts about 2 maybe 3 days. Was that period because she got last one on 28th April? Should be worried about pregnancy? When to expect next period?