I had hemorrhoids and each time i have a bowl movement i bleed?

i have hemorrhoids and ibs constipation, lately when i finally have a bowl movement first i get a sharp pain in my left lowel abdominal and the i use the restroom i bleed each time with clots of blood, this is always i get the pain in my left side. the have done test on me and do not find nothing they said is hemorrhoids and ibs, but is getting worse and the blood is a lot. i am very concern. any suggestion in what test i can get done to determine really what i have.