first of all, it's ok to drink prune juice during pregnancy. i had a lot when i was having my child. it's ormal to have constipation when you're pregnant. i blame it on the prenatal vitamins pills. for me, once i changed the brand, i was ok.
and then, don't think that you're giving the baby all the toxins! the baby do know how to get the best out of you. if you're not eating much, your baby will get the nutrition reserve you had before you were pregnant. like getting the calcium from your bones & teeth, getting the fat from your rear & your thighs! i actually lost weight on myself while i was pregnant! if you don't feel like eating anything, drink soup that is made from chicken, corn, pork, carrots, etc. & just eat rice. rice is all good.
listen to some relaxing music, and rent some funny film or tv series. you can never watch "friends" or "sex on the city" too many times!
hope you cheer up!