I lost it back in february...and still nothing!
I know I was eating very poorily last winter, hardly enough calories, working out way too hard, and just treating my body badly- but I changed that by June, and still nothing!
I'm 5'8, 140 lbs- so not underweight, I've hardly had time to go exercise anymore, so it's not working out too much, and I eat a good amount of fats (healthy kinds from nuts and oils and avocados)- so why hasn't it come back?
I'm only 16, and I could be doing some really bad stuff to my body if it doesn't come back!

I'm vegan too, and used to take iron suppliments, and they never seemed to help, they just caused constipation, so I stopped taking them. I have nutrionaly yeast, fortified cereals and soymilks for B12, and generally, I eat a lot of fruits and a good amount of veggies. So what could I be lacking? Or is my body just taking time to get things straightened out?

I'd advise you to have a talk with a gynecologist.

Have you always been vegan? I have heard that being vegan can delay your period so it may that it stopped and it'll come back on its own.

When I was having very infrequent periods, a gynecologist told me she was ok with me having 1 period per year.

I agree, talking to your doctor is the best option.

Depending on the severity of your eating/exercising issues previously, you might not get it back. Don't freak out until you talk to your doctor, but amenorrhea is one of the physical effects of anorexia that doesn't always get better even if your eating does.

It could be such a number of things. Definitely see a doctor, though. If it's something that may affect your fertility later on, you definitely want to know about it, in order to fix it now. Could be as simple as a weird puberty quirk, as you're only 16 - or it could be much more.

Definitely go see your doctor, sweetie. Good luck!