Try drinking lots of water (2ltr) a day, this will help to flush out the toxins in your body as well as in your kidneys where your adrenal glands are situated just above each kidney; the adrenal glands are often known as the fight or flight glands and if they are not performing as they should can make people feel tired and lazy.
Also take a look at your diet and try if you are not already to include plenty of fresh fruit and veg and include some complex carbohydrates in your diet; a good one would be to have some porridge with some fruit for breakfast and change from white bread to granary bread and cut out the bad fats and include some good oils in your diet like olive oil, flax oil, fish oils, Udo’s oil.
And most importantly if you are not doing it, try and do some sort of aerobic exercises in the day when ever possible.
It may be worth asking your Physician to check your thyroid gland to see if everything is o.k.
There are a lot of herbal and homeopathic medicines out there as well as over the counter medicines, but I would not rely on them solely as a cure and I would advise where herbal and homeopathic as well allopathic medicines are concerned to have a qualified practitioner prescribe them to you.