What Causes Recurring White Spots On Lips?

im 25 year old male.. i have these white looking spots on my lips.but you cant see them unit i poked my lips out l(when making the sad face or when i pucker up for a kiss) pretty much when id srecth my lips out. most of the white spots are on my bottom lip but now the top lips is starting to form these white spots too. The wierd things is i can wipe them off but only with a toothbrush) but hours later they come back. I DONT SMOKE & ALREADY gotten tested for HIV(negative) NOR CHEW TABACCO ever in my life. can you please tell me what it is Doc..becasue pretty much im scared.