Possible drug overdose?

I took half of a percocet 10 and had some Voltaren Gel rubbed on my back. I was sleeping and woke up because I was cold and started feeling like I wasn't breathing right. Like I'm seriously freaking out. I hardly ever take medicine and I'm not real sure you can even overdose on such stuff especially due to the small amount taken. Is this possible? The only other conclusion is my body has actually relaxed and I'm not use to it. I took the pill like 5 hours ago and cream was right at 3 hours ago. Somebody please tell me so I can get back to sleep, this is freaking me out.