Hello wrightjw198034, welcome to the forum, and congratulations on starting treatment
. Don't stress out, even though Genotype 3 is the most difficult of all genotypes, it's still easy to treat for treatment naive patients with the new DAA medications, such as Epclusa. So if the generic Epclusa you're taking is of good quality, your cure chances are really excellent with the standard 12 weeks course, about 90% (95% for the other genotypes).
Also, if you're undetected at 4 weeks, it does not mean that you will be cured after the end of treatment with total certainty. Cure can be declared with 99% certainty when a patient has an undetectable test 12 weeks after end of treatment. The certainty increases to 99.9% when the test yields an undetectable result 24 weeks after end of treatment, this is the golden standard for declaring a patient cured.
On a side note, if you're undetected at any time after start of treatment, there is no need to waste time and money by taking the test again until you finish treatment, because once you're undetected during treatment, you will stay undetected until you finish it.