What Causes Yellow Vaginal Discharge After Having A Miscarriage?

hi i have been through a miscarraige and a week gone friday i had a injection, because there said there is tissue somewhere but in a unknown place, i have been goingfor blood tests to make sure my hcg levels go bk to normal,at the moment there are still 17,i am just wondering if you can still get pregnant while the hcg levels r still at that level and i also have been getting someyellowish discharge, what cud it be?