How often should i have sex with my girlfriend?

My girlfriend and i have been together for 5 years, and we have a long distance relationship.We speak on the mobile phone everyday and i see her once every 2 to 3 weeksShe complains that i want to have sex with her anytime i see her and its is a big problem to her. But i said to her its not a big deal when only have sex like about 2 or 3 times a month, but she still complains to me and even considered breaking up with me because i want to have sex with her anytime i see her. What should i do?