Dear A.,
I am sure that you know that whinning is part of the human experience. But the many days of it may have a cause beyond that. I do notice that my husband's 53 year old daughter still has a certain way of whining when things are not going her way. - kinda interesting. She really hates it when she doesn't get her way, and there is a lot of hell to pay for all concerned. Oh well, just a warning to the wise.
Anyway, maybe he is tired, think of what happens around those whining days - maybe he needs an extra bit of rest.
Also, if you can't satisfy him right away, then let him cry and whine until he quits - yes it will be difficult, but whining is a learned activity, and he can learn to communicate another way too. But he won't if you fuss at him. Just get him safe and comfortable and let him whine. and cry, and whine, and he will find out that it is not the way to get mom's attention anymore. Tell youself that you are doing the right thing and that it will not harm him. Then keep a close watch so that he will not have a tamtrum and hurt himself.
C. N.