Stung on head and arm, swelling, discomfort, any otc meds?

Antihistamine: Try antihistamine and topical hydrocortisone. If the area is painful, NSAID may help also.

Bug stings: Oral,and topical antihistamines can be helpful. Oral steroids if needed will mitigate a more Severe reaction. Dakans solution can be made by diluting common bleach 10:1 with water. Dabbing on the sting can decrease the hurt quickly.

Antihistamines: OTC antihistamines are indicated but I think you will need more than the usual OTC antihistamine. My advise is to see your primary care physician or an urgent care facility NOW!