Hi Gingergirl, welcome to the forum.
First thing I should say is that drinking kelp and spirilina is NOT a good idea. In fact, it's a very bad idea. That's far too much iodine, and I don't suppose you had it tested first, did you? Iodine is just a trace mineral, you don't need that much of it. Taking it in excess will stimulate your thyroid. And, if your thyroid is struggling, the last thing you want to do is stimulate it. You could make yourself ten times worse.
Levo - which I presume is what you've been put on - is not a drug, so taking it for life really isn't that scary. It's a hormone - we call it T4. It's a storage hormone, so doesn't really do very much at all. It is converted into the active hormone, T3, as your body needs it. But, your body does need it. Every single cell in your body needs T3. You cannot live without it. So, trying to live without the levo is not an option.
There is no need to be scared. Quite the opposite. As your levels build up, confusion and memory loss with disappear, and energy will return. But, you need to take it correctly : on an empty stomach, one hour before eating or drinking anything except water, and two hours before other supplements or medication.
Did your doctor tell you to go back for a retest in six weeks time? When you go back for the test, make sure it is early in the morning - before 9 am - and fast over-night. Leave 24 hours between your last dose and the blood draw.
Hypothyroidism has little to do with what you eat. However, as a vegan, does that mean you eat a lot of unfermented soy? If so, I'm afraid you're going to have to give that up. It is 'lethal' for the thyroid, and can make you feel very ill as it will reduce the amount of hormone your thyroid can make, and how much can be absorbed by the cells. Being a vegan might also mean you have low iron and B12, and it is essential to have optimal levels for your levo to 'work'. So, if I were you, I would ask your doctor to test your vit D, vit B12, folate and ferritin.