So tired after work i just lie in bed for the rest of the day

Sounds like depression to me.

Bad food will make you feel sluggish and lazy

That's a very unhealthy cycle you're in. Eating healthy food would be a good start: if you can't manage that during the working week break the pattern on your days off and then continue. Get some exercise too, even a short work in your lunch break would help.

You could also go to the doctor for a checkup in case there's a medical reason you're so tired, but if your only life is work, recovering from work and eating rubbish food your tiredness could be verging on depression.

This isn't normal for someone your age. I think you should see a doctor. Your tiredness could be caused by chronic fatigue, a bad diet, depression, anxiety, low iron levels, glandular fever, or a combination of different things (and not to mention countless other things I haven't even listed). I myself am recovering from depression and chronic fatigue, but I'm getting better. This is how:

First of all, I agree with everyone else's comments on eating healthier. It will definitely give you more energy, no matter what the reason for your tiredness is.

Another piece of advice is to do something active when you get home from work. Now I know what you are going to say, 'But I'm too tired to exercise after work!' Well, tough. Most people think that exercise "tires you out", but actually, small amounts of exercise will wake you up and give you more energy. So drag yourself out of bed, and do something that gets your blood pumping. I'm not saying that you should run a marathon, just maybe go take a short walk around the block to wake yourself up. Pop in some headphones and it can even be a therapeutic way to shut out the world and relax.

Also, make sure you are getting the proper amount of hours of sleep every night. For an 18 to 25 year old that is 7-9 hours every night. For a 26 to 64 year old that is also 7-9 hours at night. Do NOT take naps! I know you said you don't but I just thought I should throw that in there because I can't stress enough how bad they are for someone who suffers from tiredness. They not only screw up your sleep but you become dependant on them. Take it from someone who basically just slept for two years. DO. NOT. TAKE. NAPS!

I would recommend looking into meditation and yoga and learning more about yourself.

What kind of work do you do?

Do you like your job? Look, if you're comfy with this lifestyle, there's nothing wrong about it. It's better than getting up to no good late at night. If you're annoyed with yourself for this mundane routine, try consciously changing it up a little. Instead put the laptop away and decide to take on a new hobby instead or call up a friend or relative. Doing exercise or getting a gym membership could really up your energy levels. Eating more greens as well.

Drink some coffee and stop griping.