how long till i test?!

Kirsty
Hi everyone, my cycle has always been iregular. Some are 25 days long, others up to 40. With that in mind I'm currently on day 36 of my cycle and still no sign of my period. My boyfriend and I had sex twice during my ovulation cycle, or at least we judged it by this app so I'm not entirely sure how accurate it is, but see I've had symthoms of pregnancy.
Ive had increased discharge (sorry TMI) I've felt sick maybe once or twice, plus I get these killer backaches and stomach cramps and pains, some feel like period cramps and others feel like stitches. 
So how long till I test? Should I even test at all? Help help!!