Get a nit comb - it's finer than a fine-tooth comb.
Put a dark sheet on the floor or on the ground outside (sheet, so you can wash it...)
Then, comb through your hair over the sheet.
If it IS lice... you will see evidence on that sheet pretty quickly.
It's pretty obvious if what you see is just dandruff... 
No point in going through the hassle of treatment if it isn't lice - and using it when you don't need to can make it less effective next time.
No need to throw out combs and such - put in deep freeze for a week (they say 48 hours, but... I prefer a week). It "freeze-dries" any attached problems. Then wash (after thawing).
And then... put Poppy through the 'comb-out over sheet' test too...
