I'm going to northern egypt in summer but i've led a very sheltered upbringing and haven't really travelled much

Consequently my stomach has never experienced all that foreign e-coli out there and i've never had a chance to build up a defence.

SO....., what are the the chances of me being ill in egypt? Lot of ppl have said i'll be fine if i'm careful with water, ice, fruit etc. But others have said i'll almost def get stomach upset at some point.

Any advice?

cheers