Yes and no. The e-coli you have in your gut belongs there, but, while you can get sick if you ingest your own shit. e-coli is not present in your stomach unless you eat it from improper hand washing. You just won't get as sick as if you eat somebody elses e-coli. It's a bacteria and it constantly mutates, plus there are several types of e-coli around. So you have some immunity from your own, but, if you have an abcess in your intestines and it gets out into the bloodstream or you do eat it, things can get pretty hairy, especially if people have a compromised immune system to begin with.