I'm not comfortable giving bjs anymore

So I went down on my boyfriend the other day and ended up with smegma in my mouth. needless to say I was really grossed out and it totally killed the mood for me. usually he's clean and giving head is really fun for me, but this time he just wasn't. has this happened to anyone else? I feel really grossed out and it's hard for me to want to have seen with him anymore. I Love him but that was just icky.