What Causes Anal Itching After Sex?

I am constantly getting uti's along with anal itching especially after sex. I've been on many courses of antibiotics and feel my body is being ravaged by over-medicating. Many preventative measures are out there but i don't know where to start. It's to the point where I'm scared to have sex with the outcome always the same. My husband is also suffering from severe anal itching. We've been married 14 years and have never had these problems,please help!!