5 weeks and still negative.

So if I've worked my periods out right I'm 5 weeks late, took 3 tests in the space of 2 weeks I think and they're all negative. Most recently I took one yesterday morning, thought I saw a faint line but I didn't know if I was looking at it too hard. Doctors can't get me in until next week and that isn't even definite, should I take another in a few days? And what should I do if its negative again? can people go this long (if I am pregnant) without testing positive? The longest time I've been late is probably 2 days, any advice welcome just need some reassurance xx