Is it Colon Cancer? Please help me

Hello everyone, I'm 19 years old and lately I've been experiencing stomach pains at night time. It feels as though there is gas trapped somewhere so I rub around and push gently until I pass gas or something. I had a purple slushie from sonic a few days ago and my stool was green for a bit so I just blamed the slushie. It was normal after that then last night the same thing happened with me pushing and prodding. I went to use the bathroom but nothing happened. This morning, I pooped but unfortunately it was green again and I'm having some pain in the left side of my pelvis area. Please help me, I'm scared.