Hello,
Insomnia is rarely primary. In most cases, it is secondary to antecedant cause like anxiety or a depressed mood. Since you've mentioned that it's been only the last 4-5 days that you've been having this problem, it might be related to changes in your work schedule, a stressful event at your home or work environment.
Anxiety relating something causes difficulty initiating sleep, and once that happens every night you go to sleep with the thought 'whether I will be sleep tonight, which fuels further anxiety. You have to break this cycle by planning the day ahead, go to sleep with a clear mind (by reading something light).
DO NOT resort to scrolling on your smartphone foe hours together before you go to sleep. Strictly avoid that or any other activity which stimulates your brain, such smoking or drinking tea, coffee.
And here's what we called 'Sleep Hygiene', which will aid to solve your problem:
1. Your bed should be used only for sleeping, and not for eating, watching television, surfing on the internet, and the likes.
2. The room should be sufficiently dark to augment the process of natural production of melatonin in your body (which happens at night, and light disrupts it, and hence the circadian rhythm).
3. Sleep in soft, comfortable clothing.
4. Avoid daytime napping, if you have problems with sleep at night.
5. Avoid stimulants such as caffeine, nicotine after 5pm.
6. Alcohol, which is a CNS depressant may lead you to mistakenly believe that it
aids sleep. The fact is that although alcohol may lead you into a sleepy state, it actually disturbs the sleep architecture, thus resulting in poor quality of sleep.
7. Exercise promotes sleep. But avoid heavy workouts in late evenings.
8. Avoid slipping into the bed right after your dinner. Allow yourselves at least a 2 window between dinner and the time you hit the sack.
9. Your dinner should be something moderately light, with minimum sugars, but not too light to wake you up with hunger at midnight.
10. Avoid watching/reading anything that is stimulating to the brain, such as, horror shows, melancholic reads, graphic novels.
11. Light soothing music and books can be helpful.
12. Sexual activity also aids sleep.
13. Try and keep your sleeping and waking hours fixed.
14. If you're not able to sleep, don't keep lying in the bed and try and force yourself to sleep. That never helps. Instead, get up, and read something light, write in your diary, or some such activity, before you back for another attempt at sleep.
15. If you have problems with sleep, do not go to sleep with thoughts like, 'will i get some sleep tonight', or 'If I don't get enough sleep tonight, my day tomorrow will be ruined'. These thoughts end up negatively reinforcing insomnia.
Good luck!