[m]The manga starts off with a young boys dad leaving after taking viagra so he can have a fun time and then his son is curious and takes one and is in constant pain and read the back of the bottle realizing he could be in real trouble so goes to the er and says he only wants a male doctor and is very embarrassed when the doctor has to help him get rid of the pain. The doctor then tells him he will only keep this off his medical record if he does it with him.

Sweet Boy webtoon by the Yaoi army.

That's the one! Thank you. I've had absolutely no idea what the name of it was until now.