I Don't Want to Go

After my last post about my long-distance relationship boyfriend not contacting me we sorted it out and we are happy talking and stuff and i said i would come to see him at christmas for 2 weeks and he can't wait to see me and was really happy, but now I have sort of changed my mind I want to see him more than anything but I've never spent Christmas away from my family and home and my sister said she dosen't want me to go at Christmas it would'nt be the same without me. Also going there is very expensive and i haven't really got the money atm. I don't know how to tell my boyfriend and scared that he might think i don't want to be with him as I have let him down saying i was coming before. What should I do?