ive seen girls suck a stick after it was in her anal. EEWWW. I think if it went in the chute it needs cleaning before being used anywhere else. Respect for the girl.
Never ever go back and forth!!!! In fact, don't have anal sex without using a condom. I doubt you'd get an infection that would cause infertility, but anal yeast infections, vaginal yeast infections, and BV infections alone should be reason enough not to be back and forth. If you had an infection, yes you would probably have symptoms. Your doctor will probably tell you to come back only if you notice unusual discharge, burning or itching, or an odour.
If you got an infection from it, you'd know it. And while it's not exactly a great idea, it's certainly not gonna kill you. If you have no symptoms, don't worry about it. In the future, make sure he either washes in between, or uses a condom (and switches to a new condom for vaginal) as someone else suggested.
There's no way that putting his penis into your vagina after it was in your anus is a healthy, safe, clean, or in any way good idea.
I have heard people say that if you engage in anal sex, you should have your partner use a condom for that and then he can remove it when having regular intercourse. Sounded like a good idea to me.
You can get an ecoli infection. It's caused by feces and other bacteria found in the rectum entering your vagina and urinary tracked. It can be very painful and dangerous, even life threatening if not treated. You should never go from your rectum to vagina during sex.
I have heard that it can cause really bad yeast infections etc. and it's just not very sanitary.