PREGNANCY TEST HELP

How accurate are at home pregnancy tests when done correctly?? I often wee in a cup and then test and check within the time frame. I have done tests at all different types of the day, at the start I tested mostly at night because it said it doesn't matter what time. But the ones later on I tested in the morning when my urine isn't dilated because I hadn't had water. 
I have been taking some twice a week and then waiting a week and taking another one for the past 18 weeks. 
They have all been negative and I have seriously taken like 15 of them. 
These are my last two tests. 
One the first photo had what I think is an indent like, it was a thin white line the appeared straight away. I think that's what an indent line is... 
They look negative to me, can anyone else see if they are?