Bad to hear that. I may seem to be cold in this type of situation but I think that the best way to move over is to not think about your ex girlfriend with regret. Even, don't think about her at all, because you will sink in sadness while she doesn't even think about you (conclusion with what you said). Go out, meet friends, move, do things but don't stay still.
About the link in your mind between Berserk and your ex, well it's hard (nearly impossible) to erase so keep it as a treasure of good time and sharing (or just imagine you are Guts and she is an Apostle

).
Hope I could help.