Does anyone have any tips for me who keeps losing his appetite due to fear of getting food poisoning or food contamination.

Eat. Sit with the anxiety. Repeat. Nothing is 100%. It's possible to get food poisoning, but most food will not give you food poisoning. You can never be sure either way. The best way to avoid it is to wash your fruits and veggies, don't eat food with visible rot or mold (except cheeses that are suppose to have it like blue cheese), don't eat it if it smells off,, don't leave leftovers on the counter more than 2 hours, and dispose after a week, don't eat past expiration dates (sell by and best by are not expiration dates, so don't worry too much if those are consumed past the date, cook your meat/poultry/fish (don't rinse raw animal products in the sink or place it near other foods. Clean the counters with a cleaner that kills germs when done, but don't go overboard). Most restaurants should have proper sanitation practices, and if they don't look clean (you can tell) then don't eat there. That will ACTUALLY reduce your chances. I use to work in a contract food testinging lab, in the Microbiology department. Hope this helps.

The advice I originally gave was bad. Here's something better: eat. Just eat. Better yet, find foods you think you'll enjoy and stick with them; it will be harder to make yourself eat if it's not something you enjoy. (For example, if you're a heathen who likes beets, eat beets. If the texture of mashed potatoes makes you lose your appetite, stop eating mashed potatos.) It's easier to eat things you may enjoy than try to force gross things down your gullet. You can start by eating as slow and as little as you want and work your way up to a full meal at a regular pace. It may also help you to cook your own food, basking in the aromas and being hands on with the food. That sort of thing might make your appetite grow. And remember, there are lots of things humans eat that are poisonous that we keep eating because we enjoy it. And everybody gets food poisoning, so you're not alone, and there's no huge reason to be scared.