Thinking of going vegan once I have my baby. Good idea or bad?!

Great idea.

Eat nuts, peanuts/butter, almonds/butter, cashews, walnuts, sesame seeds pumpkin seeds and sunflower seeds daily- either on their own, or in granola or cereals, or salad.
Eat tofu and soymilk, soycheese, soy yoghurt.
ALmond milk and rice milk.
Brown rice, vegetables, bananas, pasta, curries, noodles and bean sprouts, tofu soup,
lots of green vegetables, smoothies and mushrooms, soysauce, lentils, chickpeas, fava beans, lima beans and soups with these things in them.

Eat loads of coloured foods, and all kind of seeds and nuts every day, in as many forms as you can. DOn't ever eat white bread, white rice, white flour, white pasta- just eat the most nutritious foods every time you eat.
Ie, no refined sugar cereals, no sweets, no biscuits- occasioanlly is fine, but not as your meal.

I would just like to respond to one part of your description. Calcium. I think if you get a chance you should research this and you'll find that dairy products are not the most efficient way of getting calcium. The dairy industry is responsible for many mistruths about this. Calcium can be absorbed more readily from vegetables with dark green leaves, nuts and seeds, and too much protein inhibits the body's ability to take up calcium.

Becoming vegan is perfectly healthy, if you do it the right way.
Go to the library or buy The Kind Diet. Alicia Silverstone wrote it and it was what got me eating a plant based diet- the RIGHT way.
Milk can actually leech calcium from the bones. The animal protein is acidic and your body (which is healthiest at an alkaline pH) tries to balance it out by taking minerals from your bones which in turn causes bone loss. Look it up. You have to remember the dairy industry puts millions into advertisement each year to get people to buy milk. While it does have lots of nutrients, they do not always provide for the body like they should.

definitely good! i suggest getting the book "The Vegan Sourcebook" by Joanne Stepaniack. its very helpful
make sure you get all the info to be perfectly healthy!
cows milk can be damaging for your baby so make sure they stay away from it! ive done lots of reading on this, dairy is bad for young children/babies, their bodies aren't able to digest dairy and it can get them sick. as for you most people have a dairy allergy that they don't know about. good luck with the new family <3

Things like dairy fat and protein are essential for maintaining your child's brain development, bone structure and muscle development.

Seeing how you are underage and underweight yourself, it's probably not a good idea for you to be not eating properly now. Physically you are probably underdeveloped yourself.

But talk to your doctor.

I'd see a reliable nutritionist instead of consulting people on here...I am all for going vegan, I just think that you need advice from someone who has credentials that you can see =)
You're very young and your body will need extra nutrients for the baby, so you really need to consult with someone who knows what they're talking about. You could try your doctor, but a nutritionist would be better. Going vegan while pregnant, or after giving birth is fine, you just need to make sure you are well informed, and people on here can be misleading, or just flat out wrong.
Congrats on the baby =)

Good, just drink ALOT of soy milk and eat alot of soy cheese