Same here, opposite problem, when I'm stressed and or depressed, I find that diapering up, regressing and going into baby-mode actually lifts my spirits and relieves a ton of stress. Maybe you are just worried or anxious following the break-up, when I am worried about stuff in my daily life or over anxious sometimes that'll inhibit my regression time. I find that the only times I struggle to regress are if I have a full plate, lots of work or University assignments to keep track of or if I'm feverish and sick.
In any event, wait things out, deal with your stress and depression properly, maybe even retreat into some other hobbies until you feel the drive to regress again. I have faith that if you wait things out, the clouds will part and you'll be regressing and enjoying life again in no time