C172 LNDG PDK EXPERIENCED NMAC WITH TWIN WHILE TURNING FINAL AT 1800 FT.

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I WAS FLYING BACK FROM LCL FLT TO PDK ARPT. DUE TO HIGH RADIO USAGE CALLED AT 15 NM OUT; 7 NM OUT; WAS ASKED FOR IDENT ABOUT 1 MI FROM CLASS D BOUNDARY. TWR FREQ WAS VERY BUSY; GOT ANOTHER CALL FROM TWR AT ABOUT 1 MI FROM R DOWNWIND FOR RWY 2R; ASKING FOR ANOTHER IDENT. ABOUT 1 MIN LATER; I WAS ON DOWNWIND FOR RWY 2R; ABEAM END OF RWY. I RECEIVED TA; AND IN THE SAME MOMENT SAW PLANE ASCENDING TO MY R AFTER TAKING OFF FROM RWY 2R. I DIDN'T CATCH TFC DIRECTION; BUT ASSUMED CTLR WAS CALLING OUT THIS TFC TO ME; SO I RESPONDED 'TFC IN SIGHT.' LATER RECEIVED LNDG CLRNC TO RWY 2R; AS #3 IN SEQUENCE; FOLLOWING A 'TURKEY.' I STARTED TO LOOK FOR #1 AND #2. I NOTICED PLANE ON RWY AND DSNDING PLANE ON FINAL; AND THOUGHT IT WAS #2 AND #1 JUST LANDED. SOON I TURNED R FOR BASE. WHEN I TURNED FINAL I NOTICED I SLIGHTLY OVERSHOT AND STARTED CORRECTING IT TO R -- IN THIS MOMENT I SAW TWIN SLIGHTLY ABOVE OVERTAKING ME ABOUT 300 FT TO MY R. I ALSO HEARD 'WHAT'S THIS GUY DOING?!' WHICH WAS PROBABLY DIRECTED TO ME. TWIN BEING MUCH FASTER CLRED RWY LONG BEFORE I TOUCHED DOWN. I HEARD CTLR APOLOGIZING FOR THIS PLT OF TWIN. WHOLE EVENT SCARED ME A LOT; AND I THINK IT WAS MY LACK OF SITUATIONAL AWARENESS WHICH RESULTED IN THIS INCIDENT. HOPEFULLY NOTHING BAD HAPPENED; BUT THAT WAS MOST SCARY MOMENT IN MY FLYING SO FAR. AFTER THINKING ABOUT WHAT HAPPENED; I FOUND A FEW CONTRIBUTING CAUSES: 1) NOT RECOGNIZING CALLED OUT TFC. IF I KNEW 'TURKEY' WAS A TWIN; I WOULDN'T ASSUME PLANE TO MY R (TAKING OFF) WAS CALLED OUT TFC. I ALSO SHOULD BECOME SUSPICIOUS AFTER HEARING ANOTHER TA; 'CESSNA; 12 O'CLOCK POS.' THAT PROBABLY WAS DIRECTED TO TWIN PERFORMING STRAIGHT-IN APCH AND I WAS FLYING THAT CESSNA. 2) TWINS FLY HIGHER PATTERN AT PDK (2500 FT MSL.) I SHOULD REMEMBER ABOUT THIS WHEN LOOKING FOR TFC; NOT JUST LOOK AT MY ALT. 3) I SHOULD ASK CTLR 'CALL MY BASE' WHEN IN DOUBT. I DIDN'T DO THIS DUE TO HIGH RADIO TFC; AND CONCENTRATED ON LNDG. BESIDES; AS A RESULT OF SOONER OMISSIONS I FELT THAT EVERYTHING WAS OK AT THAT TIME. 4) I SHOULD BE MUCH MORE VIGILANT ABOUT LOOKING FOR TFC BEFORE TURNING AND ON BASE. I BECAME DISTR BY ACTIONS TO CORRECT OVERSHOOT; I WAS FLYING TOO TIGHT A PATTERN. 5) THIS WAS ONE OF THE BUSIER ARPTS I HAVE EVER USED; AND I WAS A LITTLE RUSTY AFTER A FEW MONTHS BREAK. ONE HR CHKOUT 2 HRS BEFORE THIS FLT WAS ALL I WAS FLYING IN LAST 90 DAYS. BEFORE THAT; I HAVE FLOWN 70 HRS IN MAY. I SHOULD HAVE CHOSEN SMALLER AND QUIETER ARPT FOR FIRST FLTS; BUT AS I CAME TO THE UNITED STATES ONLY FOR 1 WK; I DIDN'T REALLY HAVE TIME TO DO EXTENSIVE SEARCH -- WENT TO ARPT WITH LOTS OF FBO'S. LESSONS LEARNED: NEVER EVER AGAIN PERFORM ANY TURNS FROM DOWNWIND WHEN CLRED FOR LNDG WITH HIGHER SEQUENCE NUMBER WITHOUT COUNTING PLANES BEFORE ME 'BACKWARDS.' IT'S NOT IMPORTANT TO SEE LNDG PLANE; IF I MISS THIS ONE RIGHT BEFORE ME. IF PATTERN ALT AND SHAPE DEPENDS ON PLANE CATEGORY; REMEMBER ALL; NOT JUST THE ONE I'M FLYING. IN CASE OF ANY DOUBT; NEVER HESITATE TO ASK ATC FOR HELP. IT'S JUST HARD TO ASK WHEN RADIO IS SO CONGESTED. TO OVERCOME THIS; GO TO SMALL ARPTS FOR 'CATCHING UP.' LEARN MORE OF THOSE 'TFC' NAMES OF DIFFERENT ACFT MODELS. NEVER MAKE 'QUICK' LOOK-UPS IN DENSE TFC; THAT'S WHEN THEY ARE MOST IMPORTANT!