Assuming the curve is only apparent when you have an erection, you may have an injury that left scar tissue. The scar tissue prevents your penis from forming a straight erection. The name for this is Peyronie's disease. You can go to a website for information but need to see a urologist.
I haven't added it but my masturbation habits are healthy and I often take good care of my genitals. So what could be the reason...?
What are some home remedies I can try? No I don't hump on matress or floor.
The angle at which one masturbate may cause curvature.if one humps on the floor or matresses, may get distortion in penis. Only a doctor can suggest some remedy.