VERY VERY FAINT POSITIVE ON First response test. 6 days before expected period.

I'm completely new to this site but I've been driving myself mad hoping I am pregnant.. Recently I've been very tired and sluggish.. So on Sunday morning I decided to take a first response pregnancy test. It showed the faintest of lines.. Barely visable. I thought I may be imagining it. So yesterday morning I did another and exactly the same thing.. Then again today I've tested and it doesn't seem to be getting any darker although I am not expecting my period for another 5/6 days. Is it because I've taken it too early? Or should it be darkening by now? 9 weeks ago I had a late miscarriages at 22 weeks to what they believe is an Incompetent cervix as I also have a 5 year old who was born at 24 weeks and 5 days. We are desperate not to let this put us off.. And to be pregnant again would be amazing. But I don't want to get my hopes up if I'm imagining things. Any help would be much appreciated xxx