An editor's job isn't to rewrite your story, just to check the MS for coherence, spelling and punctuation and to make sure it's concise and tight, rather than rambling and redundant.
The only thing holding most authors back from doing all that themselves is laziness and the unwillingness to be ruthlessly honest with themselves. Do you have scenes that do nothing to advance the plot, or dialogue that only repeats points that either have already been made or could be better served by exposition? Can you bring yourself to throw out bits that you think read well, but don't really need to be there? Do you recognize hackneyed phrasing and cliche when you see them?
The main reason self-publishing (aka 'Vanity Publishing') was traditionally regarded in the business as amateurish was that so many new writers are not capable of doing these things (or are unwilling to take the knife to their own creations). Unfortunately, in this Internet age, email, blogging and texting have so deteriorated language skills that many young writers nor their readers even notice when something is misspelled, words are used inappropriately and punctuation is incorrect or missing altogether. I see news "journalists" and bloggers writing these days whose literacy is so questionable I'd swear their English was a second language.
In any case, if you're self-publishing online, you'll probably have to do your own editing, unless you've got money to burn, paying a professional to do it for you. Just be brutally honest with yourself every step of the way and obsessively thorough. If you publish on a site that allows reader feedback, any mistake you miss, some reader will be sure to point out to you - and probably not very politely.