Faint line on pregnancy test!

Hi everyone, I'm new to this site so hoping for some advice. I took a first response test 5 days before my period was due. I took it in a pretty dark room so couldn't really see the result but looked at it later and a faint line was showing! I know about evap lines so thought it may be that, however took another one the day before or the day my period was due (can't remember the exact day) and a faint line appeared within the test time. I have taken a few other tests which aren't first response and all have been negative. My period isn't always regular so I'm not sure what's going on! Any help would be appreciated! Thanks