Phantom smells?

For about a year and a half I have been getting these random smells come from nowhere. The scent lasts a few seconds and a lot of the time they are actually really pleasant and have been quite nostalgic and sometimes it smells awful or I know the smell but I can't put my finger on what it actually is. 

Here are some things I have randomly smelt

Ouch strawberry bubblegum

2 different types of soaps with one being imperial leather

tropical cordial

cucumber

banana smoothie

millipede

powdery mould

yucky musky perfume

cat feaces

hot chips

popping candy

pink antibiotic liquid

ginger beer

fruit loops

tutti frutti jungle chew

licorice

musk sticks

vinegar

toasted marshmallow

cherry starburst

This isn't all of them, just an example. I have been writing a list every time I smell something I recognise. I will be speaking to my GP but I was just wondering if anyone else has experienced smelling things that aren't there.