No food, however, drink lots of fluids.
Frequent masturbation can certainly be the cause of a weak ejaculation. You can test the theory by biting the bullet so to speak and masturbating only once a day or every other day.
As for masturbating too much or too often or not being able to control the urge to do so, please read the following article and thread:
Boys and Masturbation / Got questions?
The article addresses the issue of control and the need to manage the need to masturbate frequently. Doing so is not necessarily wrong or bad because our bodies have a built in regulatory feature preventing a person from climaxing too many times a day. What is important is to establish a balance between the need to masturbate in order to deal with stress, vs., the desire for pure pleasure and enjoyment.
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I hope this is of help. Got questions?