Really weird problem...?

So I'm on the third day of my period and today I noticed my underwear was damp. I was using a tampon, but I was busy so didn't really think it through and just dismissed it. Well later on I was laying on the couch with my legs slightly open (fully clothed, lol) and my hubby was like, 'Um, your pants are wet.' Sure enough, my underwear was wet and had soaked through to my pants. (Pants were only a bit damp, not wet.) What the heck is going on? Am I peeing myself? Never had this problem before?