Just Late or Need a Test??

I was supposed to start on the 15th, here it is the 18th, it should be my last day but I haven't started yet. I'm 3 days late. This app has always been 99% accurate, every so often I'll start a day early or a day after but never this long.. I've had period/bathroom cramps, my breast have been so sore for 5 or 6 days now, slight back pain, awful headaches usually at night, I've craved sweets twice but mainly just cold stuff & I've been really thirsty. Was a little nauseous once but I thought maybe I ate too much or my stomach didn't agree. For the most part, I feel normal like it's a regular non-period day besides the cramps here & there, which usually I cramp normal/sometimes they're bad, & this is like a "maybe* twice a day for not even 5 min each & more of a bathroom cramp" & I am VERY constipated, I haven't gone fully in 3 days.. which I think is why I am very bloated & may explain the cramps. I also had sex on the 15th & it felt like period sex.. meaning that is the most I've had "period like" cramps.. usually on my period, my cervix is very sensitive when hit & makes me cramp bad.. Sex now is normal. Not sure if I'm super late or should test!?

BTW, I had white discharge the 15th & 16th like I had been having/like I usually do unless I'm ovulating/that time of the month, I woke up Friday morning (17th) with a clearer/watery white discharge? I guess to explain it.. it's still like that too.