Bleeding during/after intercourse, grayish discharge, lower back pain, frequent urination, sometimes abdominal pain. What kind of infection is this?

Intercourse problem. Emily, Unfortunately, most infections look about the same since it is your body's reaction to any infection. You need to get a culture from your vagina and from your urine to figure this out. You might be having a yeast infection but you'll need to see a doctor for an examination.