Pregnant but bleeding.

Has anyone ever experienced this?! I got positive pregnancy tests 4 days ago, went to dr and confirmed it... Then the day after I started spotting... Then full blown bright red bleeding even with little clots. Called my dr and he did a blood test and called me back to redo the same blood test, my HCG levels doubled in 24 hours!! So im confused i was convinced i was having a miscarriage but my blood levels are doubling?? And now the bleeding has slowed but still bleeding. Also, im technically only 3 days late, so still VERY early.