Hi Sav,
I'm sorry your mom has negative attitude towards masturbation and you're having to be affected by that! I will say that while you have an external reason to keep it a
secret, you also have a right for it to be
private - meaning you don't have any responsibility to tell anyone else.
If you don't wash your sheets every time you masturbate nothing bad will happen, that's completely fine. Although, if you
want to wash them more I don't think you need to provide the actual reason. You could just say
"I'm sweating more at night and I have more B.O, so I am going to wash my sheets more" and I'd hope your family would respect that and maybe even think
"How responsible! Great!".
I don't know what kind of anatomy you're working with there, but at 13, whatever your anatomy yep; orgasm without ejaculation is fine and nothing to worry about.
The further explanation on that probably depends on what kind of anatomy you do have:
If you have a vulva, ejaculation is rare for
everyone, and more often is the exception not the norm. If that's what you're asking about, here's an article with more information about that:
Squirt: On Ejaculation
If you have a penises and testes, ejaculation is more common when you're younger as the age of producing more semen will be different for everyone. Ejaculation usually becomes a more regular part of orgasm during puberty then through adulthood. If it suddenly stopped or went away in adulthood, without an obvious reason (change in medication, past surgeries) that would be concerning and lead to doctors appointments to see what the cause might be. However at 13 there can be a lot of changes going on, so unless you have those body parts
and was regularly ejaculating before, which it sounds like you weren't, I'd say it's nothing to be concerned about!
More information on puberty here:
Not Everything You Wanted To Know About Puberty (But Pretty Darn Close)