When to Test?

[Mrs.Resa]

Hi everyone! I'm new to TTC and really new to online forums but i thought i would give this a try. I have a question. I bought OPKs online a couple months ago but wasn't able to use them until this month. On the 16th and 17th the tests came up positive and to make sure i tested today, which i think came out negative (the test line was slightly fainter than the control line). So now my question is how long before implantation occurs? And when should i take a pregnancy test? Thanks everyone