You would need to see a doc for a prescription for any type of drugs. What your doc could do is give you samples. If your doc doesn't have samples what they could do is if you have insurance sometimes my doc will give me a certificate that covers the cost of the co pay.
If you have a good GP doc you are comfortable with you may want to start there. If not, then go to a psychiatrist and make sure to advise of the ed and the rest of the story and go from there.
Good Luck and Best Wishes