My daughter went through a very stressful similar situation from age 3-4. We spoke to both our pediatrician (whom I love!!!) and a family psycholigst he recommended. We also spoke with our daughter's pre-school teacher. I had also sufferred the recent death of my mother who was very close to me and my daughter. We were worried about OCD and I read many books about it. It was NOT OCD. OCD can become visible at this age but OCD can NOT be shut on and off. OCD occurs all the time and everywhere. My daughter only behaved like this at home, not at pre-school and not at friends' homes. Here is what happened and then what we did and now how my daughter is developing now.
During all this time her sleep at night had become disturbed and she was waking 4 or 5 times a night and I was bringing her in bed with me or laying down with her in her bed and going to comfort her constantly throughout the night. My daughter began to wash her hands constantly - to the point that her hands were rashy, dry and sore. She also would go into a huge tantrum fit if the paper torn from a pad was ripped or not straight or had an irregular edge. She also became enraged when she couldn't cut paper properly. She changed her panties 4-5 times a day and spent too much time wiping her bottom because she said her panties were always wet (even when bone dry). 20 or 30 times a day she would tell us she had peed a little bit. If she touched her bottom outside her clothes or shoes she wanted to wash her hands. She would become hysterical if her clothing got wet while washing her hands (but not if she was playing in water or outside in puddles).
We visited the pediatrician (my partner & I). He said it is normal at this age for handwashing to become over zealous. He told Trin to only wash with water after peeing, and to use bar soap, no liquid soap, after pooping or if hands were visibly dirty. Liquid soap can dry out hands. He told her to put lotion on her hands. He gave us the name of a family therapist if WE wanted to see someone but he was not worried. My partner & I felt that further parenting advice would be helpful for us because we were growing resentful of our wonderful daughter.
My Partner & I visited a family psychologist without our daughter per his suggestion. When we described all our concerns he told us that children have children's minds and at this age imagination increases substantially along with her fears. He told us that her sleep disturbances at night were most likely linked to all her other daytime issues. He said we must work to get her back to sleeping and falling back to sleep throught the night on her own. He said once she trusted herself to conquer her nighttime fears and worries; she would begin to conquer her fears & worries during the day. His advice was: tell her everynight that we love her no matter what she thinks, no matter what she says, and no matter how she behaves and that we will never leave her. He said to tell her that we would check on her in 5 minutes and continue to check every 5 minutes until she goes to sleep. If she wakes in the night, don't go immediately but rather let her try to comfort and settle herself, and if she needs us to do the 5 minute check again. Keep doing this while slowly extending the time of the checks (add a minute each night). Always go to a check even if you think she has fallen asleep until you know she is asleep for sure. Keep a sleep log. I also was told to go out during an evening and let my partner handle bedtime and return soon after bedtime so my daughter could see I was safely back. He also suggested removing some of the frustrations. We put the scissors away for awhile. We got a ream of copy paper and put the pad of drawing paper away for a time. We only let my daughter change her panties if she had an accident and told her that her clothes would dry and it was ok if her sleeves were wet. She still threw tantrums and got very frustrated and during these episodes I would just hold her tight, whisper she was ok and everything was alright and help her to calm down.
Now at 5 years old, our daughter is amazing. She is independent, caring, nurturing, strong, willful, curious, messy, and everything I could hope my child would be. We watch her brother for similar difficulties but who knows if he will have the same troubles. We look back now and barely remember that period of our life (and it was really only a few months); tantrums, exhaustions, arguments, bad feelings, sadness, frustration, and feelings of not knowing what to do. It seems like another world. But with the advice of our pediatrician, our daughter's pre-school teacher, and the family psychologist (whom we only visited once) we found the patience, tools, and understanding to help our daughter pass through this developmental stage. Good Luck, you can too!