No period to test off

Mikey

so due to some long term issues with my ovaries my period tends to disappear for 6-12 months at a time then will make a random two day appearance before leaving again.

basically I'm trying to test if I'm pregnant or not but literally every instruction paper says 'test up to 5 days before your expected period!' Huge issue, next period will probably come in about mmmm 8 months. So when is it best to test?

Note: I am fully and totally capable of becoming pregnant, if positive this will be my second pregnancy. The first one I found out by accident when going for an ultrasound on my ovaries.