Is it bad to have sex while on your period?

"Bad" is a judgmental word for something that fails to meet an acceptable standard so whether it's bad depends on the standard you're using. There may be religions that oppose it, I don't know. It's not illegal and I've never heard of someone suffering serious damage from it. I suspect the objection for those who don't do it is simply that it's very messy.

In my opinion, it's fine as long as both partners are comfy. This may be tmi... but we just double up a burgundy towel over the sheets and proceed as usual.

MORE INFO --> Check out this health info about increased risk of STD, infection, etc. I've never had any trouble, but you should be aware and make an informed decision.
http://std.about.com/od/riskfactorsforstds/f/Does-Period-Sex-Increase-STD-Risk.htm

no But Is Not Cool !