5 days missed period, 2 negative HPT (more details)?

[Pinkbunny20]

My last period begun Nov 5, 2017.

I've used a period/ovulation tracking app for the last 9 months. My shortest cycle was 29 days. My longest cycle was 34 days. Thus my average cycle is 31-32 days.

According to the app my ovulation date was estimated Nov 23 with medium to high fertility during that week Nov 18-24. No contact whatsoever during this time.

I had unprotected sex on Nov 30 (1 week after ovulation -- app says low fertility). My partner says he didn't ejaculate inside but only outside.

I was expecting my period this month last Thursday Dec 7, 2017. It's Monday Dec 11 over here supposedly my fifth day but still no sign of menstruation yet.

I have taken 2 home pregnancy tests. One last night but my urine was more diluted. Second this morning on my first pee better concentrated. Both came out negative.

I thought I would have finally rested my worries after my negative results but maybe I still need more assurance from real more experienced women. I'm avoiding pregnancy.

I have never taken birth control pills previously and have no known relevant medical condition.

With all information above, how likely am I to be pregnant? Could I have ovulated late? Could I be pregnant in any other way? Am I stressing this out just a little too much? 

If I'm not pregnant, what could have caused my delayed period? 

Thank you for your help.

I'm 19.