Unnecessary fear and paranoia. I do?

Me and my girlfriend had a physical encounter on 31 December 2019. We used a condom, still there was no penetration and when I ejaculated later, she was wearing 2 layers of clothes and I did not ejaculate on her. In January she expected her period to start on 4th January which got delayed. Hence we took 2 urine pregnancy tests on 14 January and both were clear negatives. She got her period on 17 January which was a normal period for 4 days. In February, she fell ill with a UTI and consumed antibiotics for 2 weeks. She also had a sonography done in Feb for the UTI and is showed her ovaries to be fine and uterine lining 8 mm. She expected her period on 17 Feb but it's still not come. She had cramps and pms till yesterday but now they are also gone. She says it's normal for periods to be irregular or missed for some months and refuses to see a doctor. Even though there is no chance of pregnancy, I can't stop getting scared and have been unable to concentrate on my work. What should I do?