I think most people can relate to what you just wrote. Anxiety is on a spectrum, we all experience it. For instance, if your partner is late to come home, the thought may enter you head “what if they got in a car accident?” and just by having the thought you can notice your heart rate increase and other peripheral effects. That’s anxiety as I understand it and it’s normal. When it crosses into the “disorder” category is when those types of thoughts cause damage to one’s life/well being in a substantive way.
Good vibes to you USMC, you’re a good dude.