About enemas and why it isnt working?

ok so i have been constipated for about a week now so i tried an over the counter enema that the pharmacist gave me. its called sodium phosphates enema usp. after i put it all in i got really bad cramps and when i got the urge to use the washroom all that came out was the liquid enema stuff and a little bit of... well u know. i dont know what to do. arent the enemas supposed to help clear you out. ive also been taking this nasty lactulose as well which hasnt worked either