Okay to double down on OTC pain meds? Can I take Advil and tylenol (acetaminophen) at the same time? I have heard you can, but is it possible to overdose?

Caution. Just because a medicine is over-the-counter, it doesn't mean it is without side effects. One should never exceed recommended doses of otc meds. Depending on other health conditions, it may be acceptable to take advil (ibuprofen) and tylenol (acetaminophen) together, but you should check with your doctor. Liver disease, kidney disease, and excess alcohol intake increase the risk of adverse effects.
Yes, . Yes, advil and tylenol are not the same class of medications, so they can be taken at the same time. Advil (also known as ibuprofen) is a "non-steroidal anti inflammatory drug" or nsaid. The dosing for an adult is 400-600mg every 6 hours. Avoid this class of medicine if you have ulcers, bleeding trouble or kidney trouble. Tylenol (or acetaminophen) is in it's own class, the dosing is 650-1000mg every 4 hours, not to exceed 3 grams per day. You should avoid this if you drink alcohol heavily or have liver disease such as cirrhosis or hepatitis. Since both of these medicines are intended for pain and fever, i assume it is one of these reasons that you are taking it? For fever, it has been shown that taking them together or alternating Acetaminophen and Ibuprofen does not significantly reduce fever more than taking one of the medicines alone. For pain, there are no good studies that I am aware of to show that taking them together will give you improved pain relief.