As men get older and their prostate function changes they often experience a decrease in the volume and force of their ejaculate, even to the point of not ejaculating. There is nothing truly wrong and the literature states that women do not feel the ejaculate during vaginal sexual activity. The sensation of orgasm is separate from the ejaculation itself and is unchanged by the lack of ejaculation.
Some medications that are prescribed for the urinary symptoms that men may experience as they get older (more mature!) may have an effect upon ejaculation. Flomax is particularly noted for this. Uroxatral is a similar drug that may be as effective as regards voiding but has a much lower incidence of this untoward effect. Also, check out the untoward effects (side effects) of each of his medications, in particular his blood pressure meds, and see if one of these needs to be changed.
S.A. Liroff, M.D.