9 days late

My original start date was suppose to be the 16, according to this app, as it is normally around that time (15, 16, 17th-ish) the latest it's ever really been was the 18th. On a day that Glow said I was ovulating, we had unprotected sex twice, where there was no attempt to pull out. Now I'm 9 days late, rarely any cramping, but extremely sore nipples/breasts. I've taken about 5 at-home pregnancy test, and even a blood test at the ER, all came out negative. I wouldn't normally be worried about something like this, but about two years ago I was pregnant and tested multiple times and nothing came out positive until about 6 weeks. (I did not do a blood test that time though) I took the blood test 5 days after my missed period. Is there a chance I could be pregnant? When is the best time to test for pregnancy?