Ok so this may sound weird to you but I was having the EXACT same thing happen to me for quite a long time and it turned out to be anxiety, and it's not like I was having full blown panic attacks or anything at this point but was having breathing troubles. After I was diagnosed with anxiety I read alot and learned how to control my breathing when I was short air (espicially while working out because your doing something new your bodies not used to and change can be a definite trigger). Once I was diagnosed with Celiac last summer I did alot of research on it and found out anixety is actually a symptom... who would have thought. I have been fully gluten free for about 4 months and notice that this shortness of breath has almost gone completely away. If you want more information to see if this could be what your going through google "Air Hunger"
I know this is an older thread but BIO oil is great 3 times a day give a little massage to every part of your body with the stretch marks and they will fade to almost nothing within about 6 months.
Sorry to burst your bubble but Rice Crispies have Malt in them and in Canada they have Barley and Malt so they are not considered Gluten Free, although it is probably a very small amount of it; it is still considered to contain gluten.....BUT they now make gluten free rice crispies information on that is on the thread below