sounds like guilty conscience..which in the way in intepret it
as,seems negative.. cause it seems from my point of view that she
used u as a pillar,tried to forget her ex and start afresh with
u,realized she couldn't do it,and felt sorry for using u and as a
result "i'm not deserving of your love" phrase came out.. 
i'm not trying splash cold water dude,but i just happened to
intepret it like this.. 