Head of Penis

No, you cannot catch an STD from rubbing your penis against something unclean, unless it has JUST been covered in an infected person's blood/sexual secretions. Other infections are possible, depending on how dirty whatever you're rubbing up against is.

as for the head of your penis rubbing up against your bedsheets and pants: that's a slight overreaction in my opinion.

yeah sounds like your being a bit paranoid. you're not going to catch an infection from your clothes or bathtowel or your bed. sexually transmitted diseases are just that; they are diseases transmitted by having sex. the only other way they can be caught is from a mother to her child during birth or breastfeeding, or sharing needles with someone who has a disease.

there are lots of strange myths that fly about the place that you can catch stds from toilet seats and stuff. you cannot.

stds are transmitted through the blood, semen, vaginal fluids and breast milk of a person.