spotting

so started spotting a little over 2 weeks, the color would change all the time. last friday i had a gush of blood just come, i passed 2 large blood clots. later that night it slowed down a lot and now it's back to spotting and sometimes it's brown.. sometimes it's red or pink. has anyone ever experienced this? my doctor thinks its breakthrough bleeding but i know that only occurs when your on birth control which i am not. any ideas on what it could be? my fiancé thinks i should take a hpt bc people do bleed their first trimester but i'm not sure.