Need Opinions!!!!!

So I have pretty bad anxiety about getting pregnant. My boyfriend and I practice safe sex but even so I still get anxious. I got off birth control because I was having break through bleeding and was convinced it was implantation bleeding or some other type of pregnancy symptom. Anyway, my boyfriend and I were having sex (standing up, from behind). We use a condom and the pull out method. He always takes the condom off after pulling out so that we see the semen and know the condom didn't break inside me. He ejaculated on my back and I guess I'm just worried that it could have run down my butt crack and worked its way up into my vagina. We cleaned it up fairly quickly and I'm not even sure I remember feeling it run down my butt crack at all, but this anxiety just sucks. Of course there's always the possibility of pregnancy when you're sexually active, but does anyone think this is likely?? Also, we used a spermicidal condom.  Does anyone know of anyone that has actually gotten pregnant in a similar way? I know people can get pregnant after anal sex if the semen leaks from the anus into the vagina, but is it likely that it could run down the back into the vagina or am I being ridiculous??