bleeding after a miscarrige 4 and a half months ago

im 19... and had been with my partner for 1year., i feel pregant and then i had a miscarrige 4 and a half months ago, i was 5 months pregnant, and it didnt all go well, i went into hospital for it to be removed but it failed the first time and the second time. it wounldnt come away, it took three attemps, i felt like i was going through hell! and for me its still not over, iv never stoped bleeding since the day i came out of hospital, i stoped maybe for a week last month and had sex, striaght away i started bleeding again.the doctors dont know y! iv had a scan and nothings there, i havent a STD or any kind of infection, iv just not stoped bleeding and its reminding me every day of the baby i lost, and no one can explain whats wrong to me,im still with me partner and hes been there for me, but he wants to know too, it is affecting us both.