I believe that body weight does make a significant difference on dosage effects.
You can google adderall dosage and get a lot of info. From what I read - if the adderall is not extended release, than you should have felt a difference at 30mg. Now, if you are really, really big - maybe not?
Here again (the disclaimer), I am not a doctor. But if you were a normal adult WITHOUT ADHD, than you should have gotten a rush from the meds. If you have ADHD, the effect is more subtle. No rush, but ability to concentrate, etc. improves. If you have ADD, the effects are even more subtle since you don't have the lack of filters/hyperactivity characteristic of ADHD. The fact that you didn't feel any difference would indicate the possibility of ADHD/ADD. You can see if you have any of the symptoms by going here http://www.medhelp.org/medical-information/show/2157/Attention-deficit-hyperactivity-disorder-ADHD?page=1#sec_3761
Realize that while the above mentioned source is pretty good for ADHD, it really doesn't get into ADD. Its not unusual for girls to go undiagnosed with ADD because they are not the hyperactive little boys running around getting the attention. And if the child has enough intelligence that they are able to compensate for the lack of ability to concentrate (ya, you understand it if you are paying attention while it is being explained), but really can't quite study enough - so you get B's instead of A's. You really don't get noticed by school personal or maybe even parents. Except YOU know that something isn't right.
Finally, GO see a doctor. Quite messing around. The fact you felt nothing really is huge. Buy the book, "The ADD/ ADHD Answer book," by Susan Ashley, and you will quickly see that something like ADHD/ADD does horrible things to ones psyche. There may very well be a good logical reason for whatever your "faults" may be. There is no good reason not to find out. By the way, this is a life investment. Pick a good doctor. A psychologist or a psychiatrist. Please post if you have any more questions.