Stuttering effecting my work!

Stuttering effecting my work! Iv'e been working at Arby's for a year now and was about to start a shift leader position but then i started getting really bad "stutter blocks". I completely can't do drive- thru now because I'm stuck on the word "thank" and can't get anything out. Ive tried using starter words which helped for a while but now i block on those too! Its getting worse now cause i cant even answer a phone call because ill block and im afraid that it'll get even worse and ill start blocking in every social situation im in... please someone give me tips on how to overcome this!