Hey, I had partial glossectomy 9 days ago and my mouth was bleeding twice. Not a few drops of blood but proper bleeding. It is not so hard to stop it though.. takes around 30 min.

I wonder why does it happen?

You should check in with your doctor about this. Bleeding for half an hour isnt good. Call them and ask to get checked out. Always better safe than sorry.

Yes definitely have it checked you may have pulled a stitch. you should be careful, blood loss and the potential for infection are great at this point. Take care!