Positive pregnancy tests getting darker

Courtney • 37 years old, married with stepkids. BFP with 🌈 after first IUI and due October 2017!
When did you get a test line that was as dark as the control line? I had definite but lighter lines on 11, 12 and 13 DPO. I guess I'm getting nervous because I thought they'd be noticeably darker by 13 DPO. Period would have been tomorrow or Monday.