Are faint test lines bad?

I was supposed to get my period on Thursday. It never came.. I had a faint positive on an internet strip. On Friday I had a positive first response test..with a light line... Today I took a Wal-Mart 88 cent test.. And the line is very faint.. Should the lines be getting darker by now? I'm getting really worried... My symptoms are the same as last week and have decreased at all... I dont know what to think. With my 2 kids I always had dark lines. I should be r weeks 6 days today... Any insight? Advice?