I don't teach sexual gymnastics, but I teach sexual comfort and communication. There are hundreds of different sexual positions. Maybe you are asking her to try really wild positions. Maybe try side to side, or have her be on top of you. You can get books that describe different sexual positions also.
Sex is so fun because nature really wants to keep the species going.
Nature created it as a powerful force that affects us physically, mentally and emotionally. To the human species, sex is even more important. We spend so much time raising our children that the human bond has to be so strong, which is why the human female, unlike any other female mammal, has breasts that develop independently of childbirth. To want your husband when you re not around him and not want him when he is there might be because you are holding on to memories of good sex, but when you come home it might remind you of bad sex. Sex in marriage can fall into a routine.