Feeling unwanted :(

When my husband and I first started dating we had sex about 3x a day and he used to do so many sweet things for me. Now after being together for 9yrs and married for almost 2yrs as well as having two kids together...we rarely have sex. I want to all day long and when the kids finally fall asleep he tells me his back/stomach/or head hurts. He has also been wanting to be without me...he either wants to go or offers for me to go! I'm confused and I feel very hurt by this. I'm ashamed of myself because with the lack of intimacy I have been letting my eyes wonder...it's also been nice to have other men flirt with me. I have a hard time not flirting back because it's just so nice to feel desired by someone. What should I do?