It sounds like the smells are from someone who passed in a fire or committed suicide. If you are feeling down, have a lot of anxiety or feel as if no one cares, then you will continue to smell those bad smells.
I understand your fear of telling someone so I suggest that you either look online or look at books so you can understand that it is nothing to be afraid of. You might check locally to see if there is a spiritual bookstore and speak with someone there. Sometimes there are classes where you can meet other teens who may have the experiences you are having but are also afraid to talk.
You are becoming more aware of your surroundings and the headaches are more painful because you feel so overwhelmed.
What you can do is find a quiet place, focus on your breathing to slow it down and then try to quiet your mind. Ask to be covered in the bright white light of the Holy Spirit for protection from any negativity.
If you just want to talk to someone who understands you and what you are feeling please feel free to contact me so you won't feel all alone.