I hate to possibly make things worse, but I know when I get like that in a relationship, it's cause I'm not as interested anymore. Doesn't mean I'm cheating, it just means I'm having new exciting experiences and may be meeting new people who make me rethink my current relationship. & out of guilt I'd be avoidant and reluctant to stay in touch...which of course is only more hurtful and not right to do. Get in touch, make sure she's still interested, have a heart to heart. Be honest, tell her its ok if things need to end. You know.