Hi my name fiona

Hi im fiona im new to this site.
 Im a carer to my 10 year old son who has autism anxiety and ocd. Im hoping to get some advice as my son going through a bad time with his ocd. His is anxiety was high but thats fine so far but his ocd is very high. He keeps asking for wipes so he can wipe is arms and hands. He asks if there no germs we keep saying no but he still keeps asking every 5 mins. Then when we finally get him settled 20 mins later he back to it. Also if me or his dad comes in from the back garden he shouts have you washed your hands or if we have gone into the passage or come in from  the front garden he says wash your hands. 
Im also having problems of getting my son to play in the garden as miss all this with my son. He usto not go into shops but we have finally sorted that one he helps with food shopping he picks the food up and puts it in the trolly so we can tick that off the list. But for not going in the garden i really im struggling. Any advice or help would be great. 
We usto bake in the kitchen he wont go in the kitchen only on xmas day as he knows he can juat go atraight in the shower. This is another problem he has to have showers as well. When he gets up he has a shower then we go out he has to have a shower when he gets back and then a one before his bed. But if we dont go out he has one shower on a morning and one before he goes to bed. But he wont go to the toilet till he has to go to bed as he thinks he got to have a shower everytime he goes to the toilet. But we have said you dont need to go in shower but he gets all up set and angry. 
I miss baking with my son and miss been in the garden with him. We so have a dog which my son loves and my dog loved him going in garden and she missing that to. 
Any help advice would be greatful.