Sex and protection...

Oh God… Well for starters you need to show some respect to your girlfriend. Despite how young you are, there is still a risk that she could fall pregnant as a result of having unprotected sex. Condoms are available to you if you know where to go (and I’m not exactly sure what country you’re from). Chemists tend to sell them and in many countries even supermarkets do. If you know so little about the consequences of unprotected sex, then it is likely that you are not really ready to be having sex.

As for anal sex… I would still advise that you use protection (as a just in case thing). If not, then you will have to use lubricant because the anus does not lubricate itself for sexual practices (seeing as that isn’t its function). As for what happens… I think that is self-explanatory. It isn’t going to be all that different when you compare it to the vagina, although there are hygiene issues and so you should really consider the use of a condom (for your protection and for hers).

As for the stuff that you are finding under your foreskin is known as smegma. If you are finding smegma under your foreskin, try to be sure that you are washing your penis properly (use soap, but nothing too harsh), etc. This is a common issue and if you concentrate on hygiene in that area, the problem should go away. If not, consult a doctor.