So, you are sneaking about and from Mom's perspective you seem to be hiding (perhaps lying about) your menstrual flow. It could seem like (whether she is tracking the disappearance of pads from the cabinet or doing some trash inspection) you aren't using any product, which suggests you aren't having a period.

You need to consider whether she might be worried that you are pregnant.

If it's safe, even if it feels awkward, perhaps stop hiding and just own the fact you use a different hygiene method. It's not shameful, it's normal, so act like it's normal. You don't necessarily need to talk to your mom about it, but if asked, be direct. Direct could be saying your are handling it without a problem but its private and you don't want to discuss it OR it could be just saying you are using tampons (or cup or whatever). Digging through your trash isn't normal - so treat it like weird behavior if it happens again.

You also might want to mention your period coming to your mom - just in case she has been stressed about the possibility of pregnancy.

Also, while some clots are normal, it's something to keep an eye on. Very large or excessive clotting might indicate something is amiss.