Anxiety can definitely cause headaches, twitching & dizziness. And headaches definitely can feel worse when you cough, shake your head, bend over, etc. If I had to guess, I'd say it sounds like you're holding tension in your body. Muscle tension can cause headaches & twitching. I know because it happens to me. I get headaches from tense muscles in my neck & shoulders. I've had twitching from holding tension in areas. During a particularly stressful time in my life numerous years ago, I had a fairly constantly eye twitch. It was awful. This was back long before I had health anxiety, so I did my best to ignore it & work through the stressful time & it went away.
You might find that the headaches are coming on in the middle of the day because of something you're doing that's causing muscle tension. For example, sitting at a desk all day, staring at a computer screen, etc. Or maybe you're stressed at work or home & after several hours, it catches up to you. I would try some simple stretches when you feel symptoms coming on. Maybe go for a walk if you can. At least move around & do something, even if you're at work. This is what I've been doing & it does help. Go on Google images & search for stretches to do that target possible tension areas. (For example: neck stretches) They even have stretches for people that sit at desks all day. DON'T Google brain tumor info or your symptoms. It only makes things worse!!! Good luck!