My female cat was fixed 1 yr. ago, but now she p's on my family's clothes, why?

My Roxy girl is 3 now, she was fixed right around when her bother and her started to go into heat. so after she was fixed, she has this bad habbit of marking her terriotry by peeing on mine and my daughters clothes or blankets. I don't know what to do and I don't want to get rid of her but I don't know what else to do, I can't afford the laundry or the headache of smelling it anymore. any suggestions, please let me know, thanks!!! :)