TTC but dealing with spotting?? help?

So i've spotted 3 days within the last 2 weeks, everytime i think ooo af finally came and then bam! it goes way for another however many days and it's totally at random...i'm just really upset and annoyed by it has anyone else had this happen? I'm TTC and took tests like 2 weeks ago but it was a BFN...Arg has anyone heard of this happening what could it be?