A PA28 PLT AT SCH MISUNDERSTOOD HIS TAXI CLRNC AND TAXIED ONTO AN ACTIVE RWY.

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I CALLED UP GND WHILE PARKED AT THE FBO; RECEIVED MY ROUTING FOR MY IFR FLT; AND THEN REQUESTED TAXI TO THE ACTIVE RWY. THE ACTIVE RWY WAS RWY 28. THE ARPT HAD MOST MAJOR TXWYS AS WELL AS ANOTHER RWY CLOSED FOR CONSTRUCTION; SO I COULD SEE THAT THE ONLY WAY TO GET TO THE ACTIVE WAS GOING TO BE TO BACK-TAXI FROM THE OPPOSITE END. I RECEIVED DIRECTIONS FROM GND TO TAXI USING THE TXWY I WAS ON; AND WHAT I APPARENTLY MISTAKENLY UNDERSTOOD WERE FURTHER DIRECTIONS TO ENTER RWY 10 (TO BACK-TAXI TO RWY 28). APCHING THE HOLD SHORT LINES OF RWY 10; SOMETHING STILL DIDN'T SEEM RIGHT; SO I STOPPED; RADIOED GND; AND ANNOUNCED MY POS AT THE HOLD SHORT LINE AT RWY 10. THE CTLR SAID; 'YES; COMPLY WITH THE DIRECTIONS.' AGAIN; I MISTAKENLY UNDERSTOOD THIS TO MEAN THAT I WAS TO BACK TAXI. AS SOON AS I ENTERED RWY 10; I SAW A PLANE ON HIGH FINAL TO RWY 28; AND IMMEDIATELY REALIZED THE SERIOUSNESS OF MY MISTAKE. I RADIOED GND WHILE AT THE SAME TIME MAKING A 180 DEG TURN TO EXIT THE RWY. THE CTLR ALSO RADIOED TO IMMEDIATELY EXIT THE RWY; WHICH I WAS ALREADY DOING. I AM STILL SHAKEN AT THE SERIOUSNESS AND INDEED POTENTIAL TRAGIC CONSEQUENCES OF THIS RWY INCURSION. I FEEL THE GND CTLR'S INSTRUCTIONS WERE SIMPLY NOT CLR; BUT I; AS PIC; WAS ABSOLUTELY RESPONSIBLE FOR EVERY DECISION. I ALLOWED MY DESIRE TO APPEAR SURE OF MYSELF; AND MY HESITATION TO ANNOY THE CTLR WITH REPEATED REQUESTS TO INTERFERE WITH THE NEED TO BE CRYSTAL CLR OF THE CTLR'S INSTRUCTIONS. I WILL DEFINITELY MAKE SURE THAT THIS NEVER HAPPENS AGAIN!