"Am I loosing too much weight too fast?"
Yes you are losing weight to fast. You should try to not lose more than about two pounds a week. So try to slow down the weight loss, to a more reasonable level. One issue that some have when they lose weight, to fast, is that they can develop folds of skin. Going with a slower weight loss plan, will help prevent to that, or will even prevent it from happening.
Now vegetables are definitely healthy, however, an all plant based diet, or better known as a strict vegetarian, or a vegan diet, CAN BE healthy. But ONLY IF it's done correctly. Some of the micronutrients are either hard to get, or in the case of two, are NOT found in any plant based foods. Then there is at least one of the macronutrients, that's not found in very good supply. I've seen a lot of teens, that jump into a strict vegetarian/vegan diet, that are very poorly informed. Many getting their information, from sites that are biased, and in some cases not only biased, but are also passing pseudo/fake science of as factual nutritional science. However the same exact thing, also applies equally to diets, that contain meat, and animal products. So if you're planning to follow an all plant based diet, here are some nutrients that you need to be aware of.
Omega 3 fatty acids DHA, and EPA, are classed as being part of the essential macronutrients.
Vitamin A (retinol)
Vitamin B2 (riboflavin)
Vitamin B6
Vitamin B12 is NOT found in any known plant based foods.
Vitamin D3 (cholecalciferol), has only one known plant based source, that's derived from a specific type of lichen.
Vitamin K2 (which should not to be confused with vitamin K (more accurately what's now known as vitamin K1), is found only in dairy, eggs, meat, and fermented foods.
Calcium
Iodine
Iron (intake for vegetarians, and vegans, about a two times greater intake is recommended
Selenium
Zinc
Choline is neither a vitamin or a mineral. While choline is found in plant based foods, it's not always enough, to meet the daily needs.
No because the first week the 7lbs would have been excess fluid and you will find it now slows down to around 2lbs per week, remember it is a diet for life or the weight comes back quicker than you lost it, good luck