birth control

okay so i just started my second pack of combination pills and i usually take my pill at 10 am but i was late coming back for somewhere and had to take it around 10:50- 11:10. a couple hours later i had unprotected sex. around like 10:30 last night i started getting cramps then i started bleeding so i put a tampon in and went to bed. i woke up this morning took my pill on time then went to take my tampon and there was like this really big chunk of body tissue, like 2 inches long, and the bleeding stopped. do i need to take a plan b orrrr?