blondeguild -
ASCAP and BMI do not register copyrights.
They are performing rights organizations. By joining one of them, you give them the authority to collect public performance royalties on your behalf.
Unless you have a song that gets major airplay, you would not get any public performance royalties. (I'm talking about a charting song -- not a song that gets played on your local or regional stations).
If you want to register the copyright to your original songs, you need FORM PA, from the Library of Congress' Copyright Office. The fee is $30 per song, or you can copyright the whole CD as a collection for a single $30 fee.
If any of the songs on your EP are written and copyrighted by someone else you need to pay them a "mechanical" royalty (unless, of course, the songwriter is your buddy, and he gives you permission for free). Without going into details, you do this by getting a "Mechanical License," and paying 8 cents for each copy produced.