Anxiety hiv / stds. It will be my fault.

I had been to Pattaya - Bangkok in the last week of February. I had sex with a prostitute one night. I was drunk but I had used a condom during the entire act. However, the condom slightly slipped once, but I was able to pull it up. After coming back to India, I had stomach pain for 1 week which was cured by medication. I also have a slight back pain at times during work hours. However it has reduced after I started yoga. Now I'm getting this itchy skin at times after bath or after coming home from work. However the itchiness goes away in a few minutes and there's nothing left in that area. Is it possible that I may have been affected by HIV or any other STD? Also, since I was drunk, I'm not sure whether the condom was put by her in the correct way or in a reverse way. I'm having this anxiety at times. i feel I've done wrong and it was my first time. if something happens it will be my fault.