if you want a good nutrition based program, you could look at Gabriel Cousens' book: Depression free for life. All about food, amino acids, fatty acids,herbs, lifestyle. He is now one of the raw food gurus and a psychiatrist as well.
Whatever you do, make sure you get enough essential fatty acids, they're vital not only for your mood but also for baby's brain and eyes. I am usually a vegetarian, but had to include a fish oil supplement (I buy Nordic Naturals as it is distilled and has no heavy metals), and it makes a difference for my mental wellbeing. You need Omega 3-6-9 (can use vegetarian sources) and DHA and EPA from fish or fish oil(the body cannot make DHA and EPA from plant based omega 3 like flax seed, although flax is a good idea too.
Keep blood Sugar stable, get enough calcium, magnesium, zinc, protein (sprouts, almonds, yogurt if you eat dairy). Eggs are good for choline, which baby needs for the brain.
Also make sure you get enough vitamin B complex. Brewer's yeast is a good supplement for that, and usually has B12 added. Also helps with breastmilk supply later.
A good herbal is by Susun Weed: Wise Woman's herbal for the childbearing year.
Throughout pregnancy, I drink a herbal tea made of equal parts
Raspberry leaf (tones uterus and provides vit C and iron, avoids constipation)
Horsetail (good for veins, has lots of silica)
Lemon Balm (calming)
St John's Wort (mood stabilising)
Yarrow (helps with blood clotting)
Lady's Mantle (general female tonic)
Towards the end of pregnancy I increase the raspberry leaf to prepare for labor.
You could also check out Emotional Freedom Technique (acupressure like tapping on key meridians to unblock emotional problems) http://www.emofree.com .Manual is free.