Advice please!!!

Hello this is my first post and not quite sure of all the words used to shorten stuff but here we go...

Me (18) and my partner (19) have been together for since 18/06/10.

We both lost our "v" to each other and have been happily together ever since...

Up intill last year when I found out I was pregnant! This was an unexpected pregnancy, but 1000% wanted and cherished from the minute we knew!!! Until wesadly lost our baby on the 9/1/15 due to a medical mistake made by our nurse (that's another story in its self)...

But anyway since then I give time for my body to recover from what happened and maintain a healthy lifestyle, we've been trying to ttc again naturaly over the past few months with no luck, I've been tracking my ovulation days using glows chart,

I've took a pregnancy test a few days ago and was a bfn I'm due my af 8/9 when should I retest?