I had unprotected sex about a week ago with a girl and I had a red under the skin rash come up. Being scared and worried I message the girl asking when the last time she was checked for STD/STi and lucky enough she was tested 10 days before and her results come back the same morning I asked if she was clean (She was CLEAR) of all STDs/STis. Which should put my mind to rest, I’ve done my online research and it could be balanitis, I’ve never had anything like this before. It doesn’t; itch, burn to urinate or masturbate, I can pull the foreskin back perfectly fine, just looks as if my bellend is a little red? I would attach a picture but don’t know how! I’ve also read it could be the soap I’m washing with and so on? Does anyone have anything to help me? Thank you
Would also like to say that there is so pain / discomfort / discharge or anything else, it isn’t even really like a rash just a few odd under the skin spots I would say? I’ve read there’s a cream you can try? It doesn’t smell or anything it shouldn’t be doing hense why I think I am just thinking too much about it? I really need some advice
Certainly sounds like balanitis. You need to be on a PC or laptop to add pictures. If you are, then you should see some extra icons towards the top right of where you type, and the right hand icon (which I think is supposed to look like the sun over hills) will add images.
If it's balanitis, then these links may help:
https://patient.info/health/balanitis-leaflet
https://patient.info/doctor/balanitis-pro  
(written for doctors)
Washing (with water, no soap) daily, and taking a leak and washing after masturbation or sex will probably help, and you could also try Canesten cream or Daktarin cream. Loose fitting cotton underwear may help, and some sites recommend washing underwear with non-biological washing powder or liquid.