About the only way the treadmill would cause that problem is if you are getting dehydrated. Drink more fluids and / or eat more fruits like apples which carry water and fiber.
Put the treadmill on a plane and fly to a doctor. You’re not going to get a satisfying answer here.
I drink about two glass of water in day.
The systems are much less today. Drinking water helps too.
A hot bath soak seems to really help.
I wonder if your problem eating chocolate had to do with the caffeine in it stimulating you to have bowel movements and not feeling like you’ve gotten everything out, a lot of people I’ve talked to are surprised when I tell them that chocolate contains caffeine or could you be eating chocolate that has lactose added and you have some lactose intolerance?
You haven’t had a root canal have you?
Chocolate can cause constipation. It does in me if I eat way too much of it.
Wondering if you had an update as I have the exact same problem as you after beginning cycling. Intermittent tenesmus, not constipated at all. I do get lower back pain as well.
I get symptoms like this from time to time. My problem is intermittent hemorrhoid issues. Preparation H is the answer for me.
What type of bike is it, a road bike (w/ drop bars) or a more upright style? Where did you get the bike; a hand-me-down/bought used, a big-box store, or bought from a bike shop?
I’m thinking bike fit isn’t right, especially w/ back pain issues; get thee to a bike shop for a fitting.