Let me get this right, you are a guy who wears a dress and other people harass you - is this right? I figure you must be a guy otherwise how would anyone suspect you are gay? Unless you proposition women in public!
Well, eat smaller meals in different places! That way when you are observed eating the other diners will think it is only one regular sized meal! Then in an hour or so just move on to a completely different place and eat another small meal! Repeat as necessary!
Happy eating!