I have a problem. I get paranoid whenever I eat junk.

Well congrats on your weight loss from 220lbs that's fantastic! No wonder your getting paranoid as you probably don't want to go back there! It sounds like you've got a lot of motivation to maintain what you have achieved but that's certainly not fun to be paranoid about food that should be a treat and enjoyed at free will!
It depends, how often are you having these treat foods? And how much are you having? Allowing yourself the occasional treat is absolutely fine and a normal part of a balanced life. If it is the case that you actually don't want it because you don't feel like it, choose a healthier option or maybe offer to bring a healthier snack.
Do feel like it? Have the cake, enjoy your piece of real cake and question have I eaten a treat food before at a party? And did I gain a large amount of weight? I'm guessing probably not as you seem very motivated to maintain your weight, believe you have strong will power and try to recognise that it is food it is more calorie dense, but will not lead to immediate weight gain in such a short time!
If your worried about binging you could try eating a healthy protein meal before hand so you avoid filling up on party food.
If you'd say you were enjoying these foods maybe a little too often, try to pick/ bring a healthier alternative.
Try not to get to hung up on it though focus on the people around you and the memories you can create rather than the food.
I hope this helps

You should allow yourself a treat every now and then, within reason. Completely cutting these things out and being too tight can result in a long, boring life, where eventually, you might just binge-out from being too uptight about enjoying yourself, every now and then. I have a few friends who've done extreme diets where they don't allow themselves anything fun and they've gone totally off the deep end at times and just pigged out. Had they maintained a healthy a diet and allowed themselves something fun to eat on occasion, this, likely, wouldn't have happened.

Rethink what you consider "healthy" foods by broadening the definition. That will help you with your anxiety. Remember too that you need a certain amount of oils.

How is a slice of cake junk food?

I know exactly how you feel. I was overweight all my life. I went from 262 to 165 in a little over a year. And for a while it was like OMG I ate over my calories today. I'm going to wake up and weigh 20 lbs more. Of course that is impossible, and my rational mind knows it, but that doesn't stop the impulse. The good news is as time has gone by and I've gained confidence in my ability to maintain my current weight, that impulse is slowly going away.