1. Crying because of hunger 
Hunger is one of the most common reasons why your baby will cry, especially newborns. The younger your baby is, the more likely it is that she's hungry. Your baby's stomach is small and can't hold very much. So it won't take long before she needs another feed. If you're breastfeeding, offer her your breast, even if her last feed doesn't seem that long ago. If you're
formula-feeding, your baby may not need more milk for at least two hours after her last feed.
2. Stomach problems from colic and gas
If your baby cries a lot, but is otherwise 
healthy, she may have colic. Your baby may become flushed and frustrated,
and refuse your efforts to soothe her. She may clench her fists, draw up her knees,
or arch her back. Experts think that it may be associated with tummy problems. It may be linked to wind, constipation or reflux, when your baby brings up feeds. Remember that this phase will pass.
3. Needs to burp
Burping isn't mandatory. But if your baby cries after a feeding, a good burp may be all he needs. Babies swallow air when they breastfeed or suck from a bottle, which causes discomfort if the air isn't released. Some babies are intensely bothered by having air in their tummy, while others don't seem to burp or need to be burped much at all.
4. A dirty diaper
Your baby may protest if she has a wet or soiled nappy. Some babies don't seem to mind unless their skin feels irritated. If your baby doesn't like having her nappy changed; it may be because of the strange feeling of cold air on her skin. Try taking her to a quiet room after a feed and before bed to help her calm down and switch off.
5. Needs sleep
Your baby may find it hard to get to 
sleep, particularly if she’s over-tired. The younger your baby is, the more subtle her sleep cues are, so it may take a few weeks for you to recognize the signs. Fussing and crying at the slightest thing, staring blankly into space, and being quiet and still are just some of the
6. Wants to be held
Babies like being cuddled. 
They like to see their parents' faces, hear their voices, and listen to their heartbeats, and can even detect their unique smell. Crying can be their way of asking to be held close. You may wonder if you'll spoil your baby by holding him so much, but during the first few months of life that isn't possible. Swaying and singing to her while you hold her close, will help to distract and comfort her.
7. Too cold or too hot
You can check whether your baby is too hot or too cold by feeling her tummy or the back of her neck. Don't be guided by the temperature of your baby's hands or feet. It's normal for them to feel colder than the rest of her body. Take care not to overdress your baby, or she may become overheated.
8. Something painful and hard to notice
Babies can be troubled by something as hard to spot as a hair wrapped tightly around a tiny toe or finger, cutting off circulation. Some babies are extra sensitive to things like scratchy clothing tags or fabric.
9. Teething pain
Teething can be painful as each new tooth pushes through tender young gums. Some babies suffer more than others, but all are likely to be fussy and tearful from teething at some point. If your baby seems to be in pain and you're not sure why, try feeling his gums with your finger. You may be surprised to discover the hard nub of an emerging baby tooth. A refrigerated Shield teether could help soothe the gums.
10. Wants less stimulation
Babies learn from the stimulation of the world around them, but sometimes 
they have a hard time processing it all– the lights, the noise, being passed from hand to hand. Crying can be a baby's way of saying, "I've had enough." Swaddling also seems to make them feel more secure when the world gets overwhelming.
11. Wants more stimulation
A "demanding" baby may be outgoing and eager to see the world. And often the only way to stop the crying and fussing is to stay active. This can be exhausting for you!Try wearing your baby facing out in a front carrier so he can see all the activity around him. Plan plenty of activities. Hang out with other parents with babies. Go on regular outings to kid-friendly places, such as playgrounds.
12. Not feeling well
If you've met your baby's basic needs and comforted him and she's still crying, she could be coming down with something. You may want to check her temperature to rule out a fever and be alert for other signs of illness. The cry of a sick baby tends to be distinct from one caused by hunger or frustration. If your baby's crying just doesn't sound "right," trust your instincts and call or see a doctor.
Best of luck !
