I have been spotting four days with mild cramps and back pain i had sex on the 24 but he did not ejaculate inside me what could this be?

Multiple things: If you have sex without a condom you can still get pregnant even if there is no ejaculation- there are sperm in the precum that would be present. You do not say where in your cycle this occurs so your symptoms could be beginning of a period, implantation/ pregnancy,an early miscarriage, an infection, a sexually transmitted disease, etc. See your MD for evaluation of cause