You will find its a Herxheimer reaction (healing) which will go in time. Your body is removing rubbish which takes energy. Also please take your juice a small mouthful at a time and swish it around to break it down with your enzymes else this can cause more problems with the stomach.
im really no medical expert but i am a regular juicer myself and yes i am a bit baffled by the info you give. If youre eating a substantial evening meal digestion naturally takes up a lot of the bodies energy so you feel sleepy. I think you may get more benefit from your juice if you drank it before a meal, up to an hour before, you are likely to feel less hungry and consume less solid food. Juice is a meal initself and although it takes little engergy to digest it should be consumed slowly and treated more as a meal. Im a keen juice faster and when i do it properly i feel full from juice, i think 'doubling up' on a meal may contribute to your tiredness?!?
Wish i had more hard facts to help but try swapping the juice round with the meal in advance. Youre right juicing should give you more energy...im sure in the long run it will be beneficial to health. The other thing is detox symptoms....boosting health gives initial detox symptoms which include all sorts on nasties, film on tongue, compost breath (sorry) the end results are worth it !!!! Emma.