Severus's (first) Mistake

COMPLETED
The one thing Severus Snape can't stand more than anything else is the idea of James Potter and Lily Evans getting together. But what if, he's the very reason they got together in the first place?
-Takes place in 6th year (Marauder's gen.)
-Mainly fluff (no tragedies)
-Basically James and Lily getting together
-I own nothing
-Sorry for typos, OOCs and plot holes.