Hello, I Have Had A Weird Pain In My Lower

Hello, I have had a weird pain in my lower right part of the stomach, which also feels like a tightness and sometimes spreads round to my back. It has lasted about a week or so. I haven't been to the toilet much but the last time I did I found a little bit of blood on the stool. I haven't been to the toilet for about 3 days and I tried to go today but felt constipated. I'm curious to what this may be. Thanks.