When should I test?

I don't remember my last period, I don't believe I had one in July and I haven't had one in August but I'm definitely had one in June. I started Vyvanse in July and was majorly slacking on taking birth control. I've been back on birth control since the first week of August. I tested Friday and it was negative but I still haven't had my period. When should I test again?

I know medication and being on and off birth control can mess your schedule up. Please be nice :)