You're just as choosy about finding the right job as the interviewer is about hiring the right candidate. Don't whine or show that the search is upsetting you. If you've already fielded an offer or two,you might say
" I have had an offer.But the situatioin was not right for me. I'm especially glad that I didn't accept, because I now have a shot at landing this position."
It's important to tell the truth, however, because the interviewer's next logical questions may be the following:
who made you an offer? For what type of position? At what salary?
If you've already lied, you're in hot water now! some interviewers will consider any admission of lying in these circumstances your "voluntary" offer to end the interview!
Many interviewers know a great deal about their competitors and which positions they're trying to fill. If you did the smart thing and told the truth, feel free to name the company.
It's important to stress that the position you turned down was very similar to the one you're applying for now. After all, if the job you are currently interviewing for is perfect for you-as you've undoubtedly already told the interviewer three or four times - why would be at all interested in something very different at the other company?