I have been up for three days. Tried Lunesta, (eszopiclone) Ambien, dphnhydrm. Elavil. Tonight doxylamine succinate. I took 50 mg ~4 hrs ago. Can I take 1 more?

50 mg is max. 50mg is the max recommended dose for insomnia using doxylamine. I would recommend consulting your physician for an exam - possibly even a psychiatrist or sleep specialist to determine why you haven't been able to sleep!