When to test

Alyssa

I got off the nexplanon July 10th & have been trying since then, i had my period in July and haven’t gotten a period at all this month , this morning i used the bathroom & when i wiped there was a pink tint on the toilet paper no blood or old blood and was only there when i wiped this morning . When would i be able to test last test i took was 8/17 and test was negative