I wouldn't worry about it. I'm sure the risk of HIV transmission by contaminated in-the-ear earphones is zero or close to it, even if the previous user had HIV, and even if such a person had a wound or blood in the ear. Your gastrointestinal symptoms undoubtedly are coincidental.
Good luck-- HHH, MD
the incident happened about 4-5 days ago, and both i and my fiancee have been having some stomach discomfort loose stools.
You probably just got a virus. STDs are by definition sexually transmitted - you definitely can't get anything from using someone else's headphones, or touching, hugging, etc.