Who knows. You are putting or did put yourself at risk for a STD. Go see a doctor. Use a condom next time, always.
Hi, most often topical irritations like your describing would be fungal related. Since the sores are all over the place it does not appear herpes related as are side specific but thats not saying that one or 2 may be herpes. Testing is the only way to confirm.
The stinging in your urethra could be from contracting a UTI from the anal sex and also may be an irritation from a yeast infection contracted from her. Its possible that the fungus is now around her anal area as well.
The anal canal is full of different natural bacterias and if youve picked it up in your urethra youll for sure need to see a doctor for testing.
On a side note. With all your unprotected sexual activity with all these different people, you should have a full panal std testing to make sure you dont pass something on to new partners. Really start using condoms.
There really isn't enough information on your post to make any kind of a responsible guess about what your symptoms are. We can't diagnose you on a forum, I'm afraid. Your symptoms warrant examination by a medical professional. I recommend you ask your partners to get tested as well.