Daniella, normal walking can be really hard with this PN thing, i used to avoid it as much as i could when PN struck, but i use to love walking before so i thought of just going around to my local pool [all weather pool] and just walk up and down the lanes at your own pace, plenty people do it for all sorts of med problems, i found it best to get there real early in the morning before the swimmers come though, great cardio excercise, good for blood circulation and its non weight bearing so your feet shouldn't hurt you like walking on normal hard surfaces, i made some friends there, the social thing is an extra benefit as well.
I wish you well too
Brian