Pregnancy scare

Hi everyone, I don’t have anyone to talk about this so pls help me. I had sex on 20-21-22 july, this was 27th-28th-29th days of my cycle.(My cycle is usually 28-30 days long, therefore at that time i was absolutely sure that my period would start soon.)
Fact: we used condom, I’m also sure that we used it properly, we also checked once ( did a water test) and everything was good.
But on 24th July i found out that i had some Urinary Tract Inflammation and i had to take some medicines. This month was hell for me, my sleep schedule was ruined, i was so stressed about upcoming exams.
SO, its been a week and my period is late, today is cycle day 38.
NOW I’M PANICKING- why am i late? Its too early to do pregnancy test so pls help me.