there are many herbs that can help you.
For adrenal fatigue, you could try a blend of licorice root, gotu kola, siberian ginseng and ginger.This addresses the low blood sugar, exhaustion and adrenal fatigue. Check with a herbalist for dosage in pregnancy.Licorice increases the effectiveness of adrenal hormones as well as mimicking the action of these hormones. It has been shown to help overcome adrenal failure. Too much licorice in pregnancy is usually not recommended, but this is based on the extract (a study found that scandinavian women who ate lots of licorice extract sweets had a higher risk of preterm labor), never the whole herb, which is safe, especially when used in a blend.
Gotu Kola does a similar thing, it builds adrenal health.
Siberian ginseng normalizes abnormal blood Sugar levels and gives general strength.
Ginger indirectly helps, as it increases nutrient absorption and facilitates the usage of energy stores.
Astragalus root is another excellent herb you could check out.
Also make sure you get good nutrition. Add some DHA to your diet to avoid the risk of postnatal Depression which has been linked to depleted fatty acid stores.
Susun Weed's postpartum Depression brew:
1/2 oz dried shredded licorice root, 1 oz dried raspberry leaf, 1 oz dried, cut rosemay leaf, 1 oz dried, cut skullcap. Mix, use 2 tsp per cup of boiling water, two or more cups a day for up to 2 months postpartum. (Infuse for 10 minutes)
Drink raspberry leaf tea (1tsp per cup, infuse 10 minutes) three times tea daily during pregnancy to tone the uterus and make for an easier delivery. I drink a blend of raspberry leaves, nettle, lemon balm, yarrow, and horsetail as a general tonic in pregnancy and had an easy delivery first time around.
Squawvine has a similar effect as raspberry leaf.
Homeopathy can be very helpful for pregnancy, birth and afterwards, too. Kali phos is a remedy for exhaustion in labor, but do read up and compare to the symptoms you had last time to prescribe correctly. Ginseng can also be used in labor to increase energy, traditionally women use a piece of the root to chew on during the entire labor. Don't take teas or powders, tinctures are ok.
Read "wise woman herbal for the childbearing year" by Susun Weed, and Miranda Castro's book on homeopathy for pregnancy and birth.