This may be a fungal or yeast infection. Fungal infection may cause irritation and thinning of the affected skin. The areas are usually reddish and they may be itchy. There may be some mild scaling and due to itchiness, there may be excoriations and weeping. I suggest that you have this asessed by a dermatologist. You may need topical medications (antifungal medications ) for this.
Also, is your blood sugar well maintained? Are you taking any medications for this ?