Two points I want to reinforce:
1) The previous poster was correct: it takes up to a week or two for DHT levels to get all the way back to "normal", so I doubt that being without finasteride for two or three weeks will be much of a problem.
2) You screwed-up BIG TIME when you continued to use the same daily dosage, when you first realized that you were going to run out! You should have IMMEDIATELY started stretching it out by cutting the pills into halves or quarters, taking them every other day, etc. etc., and it would have had virtually no impact whatsoever on how well the drug was working for you. If you had done that, you wouldn't be left now with no finasteride at all to take!
Bryan