Dairy/egg-free peeps, this NHS leaflet is a good guide to challenges and reintroduction of excluded foods. Dairy-free seems to be working out really well for us. J had his first bottle of Neocate last night and slept all night and without the early morning screamathon too. 
Fatima if you can rule out tiredness caused by illness such as anaemia or thyroid issues then there are still plenty of avenues to explore. The most obvious one is are you getting enough sleep? Is the sleep you are getting good quality? Sleep hygiene techniques such as no screens in the run up to bedtime can help. Paul McKenna's sleep CD is good for relaxing. I quite like Rescue Remedy Night, I'm not convinced it actually does anything but it tastes nice and can become part of your own bedtime routine. I have taken to reading slightly boring books at bedtime such as popular science or medical books as I don't get too engrossed in them and stay up to read them.
For a while I fell into the bad habit of self-medicating with caffeine to keep me awake in the day and alcohol to help me sleep at night but they just become a crutch that doesn't help long-term. Now I avoid caffeine after 2 p.m. and find that anything more than two or three units of alcohol seems to cause me to be awake in the wee hours, usually fretting.
Exercise can be good for tiredness too (not too close to bedtime though) as it's invigorating at the time, it improves sleep if you're physically tired as well as mentally tired, and it can cause a marked improvement in mood. I do the 30 day shred a few times a week, it's only 20 minutes of exercise but I have noticed improvements in mood, fitness, toning and sleep.
I do wonder sometimes whether diet plays a part. I cut out most processed food and sugar last summer; I also cut down on wheat and dairy. The health improvements I have had have been quite remarkable: reduced nasal congestion, IBS completely gone, no more period pain, joint pains have stopped even from my massively damaged ankle, asthma symptoms have declined, skin and allergies improvements, more stable blood sugar, less dental plaque, etc. Clearly I had a problem with dairy or gluten or something that was contributing to inflammation and causing a whole host of problems. But I didn't even know I was sick until I sorted my diet out. Now I feel so much better about my health losing 30 lb of 'baby' weight didn't hurt either.