46 year old male and regularly has little to no ejaculation during an orgasm. should he be worried. ?

Not necessarily: Unless this is a change in your normal volume of ejaculate or if you may be dehydrated, this is most likely of no significance. If you have difficulty urinating, then there may be some early symptoms of an enlarged prostrate. See a doc ASAP if there is pain, blood in the ejaculate, or if there is a change in color or odor or If trying to achieve pregnancy w/o success.

Should seek help: It's not likely urgent but sometimes low ejaculate volume with be a signs of other diseases that could be affect the prostate or seminal vesicles. It can also be a signs of issues with nerves in that area or even a medication side effect(though doesn't appear to be the case with you). So it would be wise to make sure there is nothing else going on. A urologist would be helpful in this case.