When my girlfriend and i have anal sex she bleeds and i want to fix it. we us lube but i have a large penis and only ejaculate with hard sex?

Doctor can examine: Not good. Anuses are not designed for in-and-out sex. Just like in any big city, some streets are one-way and some streets are two-way. A vagina is created or evolved to be a two-way street (penis in, baby out). However, the gastrointestinal tract is designed to be one-way, with an opening on each end. Food goes in the mouth and the brown stuff goes out the butt. (An exception is when one vomits.)