What Is The Treatment For Constipation?

Hi, there. I was wondering if you could help me.
Earlier today, I had to go to the bathroom but it was far too painful to pass faeces that I had to stop. When I wiped, the toilet paper was clean and there were just four or five small pellets of poo in the toilet, they looked similar to larger rabbit droppings. All day, it's been far too painful to do anything and I've had to continue stopping myself doing the toilet. I'm fine passing urine, but when I try to pass faeces it feels as though something has come out of my anus and then stopped. I have never stuck anything up there and I eat plenty of fibre so I am confused as to what it could be. I'm at the stage that I'm too scared to go to the toilet because I end up literally crying in pain and I feel dizzy and sore afterwards. I have also been getting pains at the lower part of my spine since this started.