Sex isn't good at all

My wife does not like having sex. She frankly told me that she is losing interest in sex. Our sex life didn't start well from the beginning. She only likes one position, the missionary one. She doesn't want to be on top because it makes her tired. She doesn't want me to come from behind because she doesn't feel good. She doesn't blow me because she thinks she feels nothing by doing that. She could only reach orgasm from the missionary position. And it is not from penetration. I know it is from her cl*toris. We have sex 2-4 times a months. Most of the time I do it with my hands. And she knows it. She doesn't do anything or say anything. She just pretends she doesn't see.

I don't know what I can do to improve sex. I can't get her excited. I had 4 girl friends before, and I was pretty good at that. So I don't think it is my problem.

Is this normal to women? She said she had so many things to think, like work and study, just not sex.