What Causes A Clear Discharge With Streaks Of Blood?

hi am a 23 yr old female i have had a clear discharge 14 days ago the the next day i had a clear discharge with streaks of blood i didnt think anything of it the day after i started spotting and spotted till the 24 i went to my doctor she said it was ovulation bleeding but i still continued i have been bleeding for 12 days now minor clotting and back pain can you tell me whats wrong with me