Why did you take plan B when he used protection the first time? I guess he put his penis in you unprotected briefly the second time so that worried you. But you seem to really stress in the way we see those who suffer from anxiety every time you have sex. You've overused plan B. I 'guess' I can see taking it the second time but really, I probably would have told you not to.
If you are worried about pregnancy, why don't you get on the pill?
Anyway, ya. What happens every time you take Plan B and with you, it would be X 2 so even moreso, you get a big jolt of hormones into your system. That's how it prevents conception. But it also leaves a ton of hormones for your body to deal with. So, periods can be irregular for 2 to 3 months with taking plan B once, and longer since you took it two times in a short span. You do not need to take anymore pregnancy tests. But you do need to work on your anxiety.
I would not have sex again until you get the anxiety under control. You need to let your body even out hormonally. You're not pregnant.