It is unusual for hot flashes to persist with this severity for 20 years. Older women can still have them but they usually become less intense.
Many anti-depressants are being used as an alternative to estrogen for hot flashes, so this is a bit unusual.
On the other hand, some of the anti-depressant medications can cause sweating, so it is important that you have a complete re-evaluation by your medical doctor and psychiatrist.
Yes, there are other medical reasons for hot flashes, therefore I do think further testing and evaluation is indicated.