In a sense, yes.
The detergent you're using could very easily have given you a yeast infection. This is doubly likely if you're wearing non-cotton-crotch panties on a regular basis.
When you're out and about, you sweat. Your thighs, big or small, do a relatively effective job of trapping that sweat between your legs. That sweat could be making you itch in and of itself, or it could have provided the sort of moist environment yeast thrive in.
If you've never had a yeast infection before, go to the doctor. If you have and you know what to look for, bust out a mirror and look for discharge, then pick up some miconazole.
Good luck (and definitely think about changing detergents).