Does Emergency Contraceptive Pill Cause Prolonged Menstruation?

i am 23yrs old, 5'5, and maybe 110lbs. i have been on my period now for 10 days, im feeling light headed and really tired. My last period was 4/15 and ended 4/20 which made my expected ovulation date 4/29 i did have sex on 4/25 and took the plan b pill within 72hrs.....could i still be pregnant or what could be the reason i am having this irregular period..cant see my dr. till 6/6...please help