What to do?

My wife and I dated for about 6 years. Everything was great back then. After that we lived away from each other for two years. We were still in a relationship during that time. We survived and decided to get married and did. Soon after marriage, physically things changed drastically. After almost 3 years into marriage, even though emotionally things are okay, physically not so much. We rarely have sex, like once in 2-3 months and that too when I constantly insist on it for months. Before marriage, we used to have sex like almost everyday. Our physical compatibility was one of many things I liked about us and made me feel we should get married. I love her but I’m unhappy. She’s great otherwise and very caring but I feel I cant live like this. We casually discussed this issue multiple times, and she says with age sex desire goes down. She’s just 31 and I’m 30! I haven’t seen any decline in my sexual desire so far. If you are thinking she might not be showing interest because of my looks, may be. But I’m a decent looking guy and I stay shredded with 6 packs abs year round. I compete in bodybuilding shows as a hobby and have been consistently hitting gym for over 10 years. I manage to get compliments from girls from time to time. I always had been honest with her, and never cheated. So, I’m not sure what can I do in this situation. I’m feeling totally lost. Have any of you experienced something similar? I need some advise. I have never talked about it to anyone else other than my wife. Thanks!