why won't my tampon go in all the way??

This may be a really stupid question but bare with me. 
I'm on my period and when I insert the tampon it doesn't go in as much as usual. I tried to push it it further and it's feels like the tampon is pushing against something hard. And it's not going in all the way and is uncomfortable. Is it just bc my cervix is really low and hard bc I'm on my period?
Anyone have this happen before ?