How can I get my poop firm?

I've been having problems pooping lately and I'm not sure what the reason is, I went to the doctor and was told that I needed more fiber so I did as I was told and ate more foods with fiber in them and even fiber bars but I still have the same problem, it still hurts when I poop, when I poop it feels it like there are sharp little blades in it and sometimes I end up bleeding.....please if anyone has a answer to my question please do so to tell me, I would really appreciate the help :)