Hi, Two Nights Ago, I (19 M) Had Sex With

Hi, two nights ago, I (19 M) had sex with a girl and I lost my virginity. I did not use a condom although I know I should've. I was wondering however since then I lost my appetite and I am not as hungry as usual, is that normal? I am very scared that I might have HIV or an STD and I plan on getting it checked out by a doctor today!