Has anyone has these experiences with Citalopram?

Nausea, drowsiness, and some trembling may be normal side effects of citalopram. This is why it is often recommended to take citalopram before bed to avoid daytime nausea and drowsiness. However, your symptoms sound rather severe and may be indicative of serotonin syndrome caused by too high a dosage. The onset is rapid and can cause headaches, pupil dilation, tremor, and may even be causing your "euphoric" mood (a phenomenon called hypomania)! The happiness you feel is probably due to side effects, as the drug can take several weeks to reach full efficacy. You should contact your prescribing physician ASAP as serotonin syndrome may potentially be quite dangerous. If you are taking any supplements that contain St. John's wort, this can result in a reaction leading to serotonin syndrome. Regardless of whether this is serotonin syndrome or not, your medication needs to be adjusted if your side effects are this severe.