Size 18 had 3 kids how do I get rid of this floppy belly.

Hi ladies has anyone got a saggy tummy I feel so discussed in myself for getting a floppy belly. My SO tells me to just keep doing exercises and do them better and I am trying so damn hard I weigh 14 stone, I have already lost a stone but I can't seem to go any lower and now I feel like giving up, I have endometriosis so I can't do sit ups as the pain is so bad any help and tips please? I'm going anonymous as I'm to embarrassed by this x