You can be a DL and not have it be sexual, me not you. If you're just wearing for (emotional) comfort/fun, I'd say you fit the definition of a DL. Ok, onto your main question. How's your relationship with your Mom and why do you want to tell her that you like diapers? Your answer to these questions determines what my advice would be. If your relationship with your Mom is bad, don't tell her, it's just not going to go the way you want it too. HOWEVER, if your relationship with your Mom is good, you might benefit from telling her depending on the reason that you're doing it. Is it so you don't have to sneak new diapers into the house and dirty ones out to the trash? Is it so you can wear comfortably around the house on a day off without her noticing that your underwear "looks a little funny?" Is it so that you don't have to be paranoid about her possibly finding a wet one in your room that you didn't have the chance to throw out because you were scrambling for school/work? Is it because the fear of her finding out about your diapers and confronting you over it is stressful enough that you'd rather get it out of the way now rather than later? If it's any of these reasons, you might benefit from telling your mother and just eating the awkward conversation now on your terms instead of later on hers. There's no easy way to do this though, and the best way is to just do it when she's in a good mood and you both have some free time. Offer to answer any questions she has (and believe me she'll have plenty,) and then actually do it. The biggest benefit your going to get out of this is not having to sneak your trash out in the middle of the night, not having to sneak new diapers into the house, and not having to worry about your mother questioning you later. Oh and remember, if she questions you later, you'll be having the exact same awkward discussion on her terms instead of yours, and you won't have the leverage that you have now. Since you seem to wear for comfort and not for purely sexual purposes, I would say that the awkward conversation is likely worth having, if only to avoid the stress of "what if mom finds out" hanging over your head constantly. Once she knows that you're telling her now so that she doesn't skydive to conclusions later, the benefits of the conversation basically are that you don't have to deal with hiding things as much as you would otherwise. Note that not hiding things is obviously not the same as granting you permission to be a slob. You still have to maintain your diapers, (get them yourself, bring them into the house, take them out to the trash, etc.,) and not just leave them lying around or anything like that, you just no longer have to hide your trash, or packages, (no more than you would want to at least,) or lie about what you went to the store to buy/ordered online with your money, etc. Oh, and there's one more benefit you have working in your favor: You're 19 in 2016 instead of 2001 or 2006. 10-15 years ago it was a lot harder to open up about this. Today people in general are more open about their sexuality, and even though this isn't sexual for you, there's a lot more information available online for people who are curious about AB/DLs that's readily available to the public, and going after someone for a different kind of underwear is frowned upon in a way it wasn't before.
Also, you can always point your mom to this forum's friends and family section for curious family members who want to understand what AB/DLs are, and why their loved one considers himself or herself to be one if she's truly curious about learning more should you open up to her. Just my thoughts on the subject.