Hello, I have a 3 week old baby who seems to have started straining on and off for hours at a time. He seems to be able to poo twice a day and they are very soft and normal yellowish in colour. We are mixed feeding as I couldn't keep up with demand initially so has formula and breast milk. We wind him during and after feeds and he always has a good burp.
I'm beginning to get concerned now with the straining as earlier on he woke up straining and I went to comfort him, he strained so much he made himself sick twice, yet hadn't fed since 3 hours before 
Is this usual, does it happen to newborns? Is there anything I can do to help him?