Had my period & a cold, how likely pregnant? Pls help

[rinbnt]

So i used a fertility app that said i wasnt fertile, maybe i didnt read it correctly. Had unprotected sex on march 3rd (apparently that was ovulation day) i expected a period on march 13, but ended up with my cold getting bad and last the whole week.
My period came march 17 on its own, 1st day heavy cramping as usual, felt almost dizzy from a lack of food in system.  Thought it may have came a little late due to the severity of the cold. For a moment i thought it could of been acute bronchitis, not sure didnt go to dr. Period lasted 6 whole days, appeared normal, went from heavy to medium to light to spotting flow with cramps.
Do u think there is a high chance of pregnancy? Or a chance at all?
Not trying for pregnancy.
Im in mid 20's, no known fertility issues