How hard do you find it when youve just broken up with someone?

I finished with my girlfriend of 6 months a week ago because i didnt feel i loved her enough but im falling to pieces over it. She is heart broken and i hate myself cause i obviously care about her a lot. I cant think of being with anyone else and currently aint seeing the light at the end of the tunnel. Just looking for some people that have been in similar situations to shed some light and how you pulled through? Im even questioning getting back with her and trying to work it out, can you learn to love someone? Although i dont want to get back and cause her further heartache down the line, help!!