My baby just crys all the time... WHY !!!!

Emma

So my baby is 4weeks old an since she's been born she seems to cry even when I have gave her bottle nappie change her so then I'll try an put her in her crib but she will start to cry right away.. She seem to be a bit better when I pick her up an hold her but my doing that is hard as I have a toddler an I feel bad on her as I feel I can't do anythink with her like I did before... as anyone had a baby like mine if yes what did you do ??