There is an interaction between grapefruit and almost every medication known to man. When it come a to mental health medications grapefruit is a very serious danger. I am glad you are ok and have patience because things will go back to as they were. Grapefruit and st. Johns wort are to things to completelt avoid while taking zoloft and/ or other mood balancing/ altering medicines.
The above say it all, though St. John's Wort isn't the only thing to avoid -- it's because it affects serotonin, but so do several nutrients or plants used in medicine as well as a whole lot of meds. Combining substances that affect serotonin is discouraged. But something else -- you say you were adding grapefruit essential oil to water. Is that right? Most essential oils are not edible, they are used for topical purposes. Some are edible, but if you want to add grapefruit to your water you add grapefruit juice or concentrate to your water, not essential oil. Folks, if you don't know how to use traditional medicine, do your homework first. This is for others, since it's been made clear already that those of use who take medication have to be careful of using grapefruit and the timing of it. I'll also add, you don't really lose weight by looking for magic bullets. Even when they help, they only help temporarily. The only way to permanently lose weight is to change your diet permanently and increase your exercise so you alter permanently your metabolism.