Toph99, yes, I believe that teens have stress, and I think that it is as important as adult stress is (or should be treated as such).
Teens stress over things that adults frequently discount, but that doesn't mean the things are any less important. Teens also stress over many of the same things that adults stress over (and often compound their own problems with worries about things that are affecting their parents, i.e., job loss, drug/alcohol problems, divorce). Adults don't make it any easier for teens by laughing it off or trying to deny that the stress is there.
Not my style, either - my kids have always said that I ask way too many questions about "what's bothering them" - but my son does come and ask my opinion about things (now that he's graduated from HS and realizes that parental units do have some sense :Q ).
You may want to approach your mother again about the problem, but this time, start with an explanation of your symptoms and your concerns. It is possible that your mother saw your comments as a generalized "theory of life" idea, rather than a specific complaint about a problem involving yourself. (Still wasn't a real good idea to laugh about it, IMO, but some people don't always think first.)
If you get no help there, check with a trusted school counselor or teacher, or talk with your religious mentor (if you have one). Anything that is serious enough for you to worry about should be dealt with, not laughed off.
Lady Niniane