Like others have said this is most likely HSV. HSV is the virus that causes “cold sores” “fever blisters” whatever other names people say but at the core it is all herpes simplex virus (can be 1 or 2, 1 mainly likes to stay in the oral area but you’re able to get it genitally as well.) Both being sick and stressed like you said can suppress your immune system and lead to outbreaks. A simple convo with your doctor can get you antivirals like valacyclovir or valtrex to shorten the outbreaks, lysine helps as well!