Create a new Apple ID that only they have access to and reset your phone to that ID, then lock it down again. You can also go further with other settings then like using a DNS server that allows you to block the domains of problem sites, stopping you from bypassing the lack of apps with websites.
Also, maybe consider an iPad and throwing away the iPhone. It's bigger and harder to compulsively check and you can't carry it in your pocket. Do your banking on that, bin the iPhone, carry a dumbphone all day instead. If you can break the habit of pulling out your phone to check it you'll gain a bit of breathing space for your compulsions.
I know multiple people with OCD and anxiety. For some, professional treatment and medication works well. For others, the only thing that really works is cognitive behavioural therapy, and finding a system that works for you is going to be trial and error.