What do brain zaps feel like?

I have no idea if I'm what expriencing is brain zaps or not. About 2 weeks ago I stopped taking 60mg of duloxetine and started taking fluoxetine 20mg. My doctors made a mistake and thought I was only taking 30mg. Anyway safe to say after a couple days the fluoxetine got upped to 40mg due to my constant anxiety. I started to feel better but I keep experiencing this thing and idk what it is. I'm unsure if I was experiencing it before withdrawals. This is because I thought it was heart palpitations and while it sometimes involves it I've discovered it actually isn't. And I can't remember if what I was experiencing on duloxetine was this or was actually heart palpitations. It's like this constant pulsating feeling and it feels like it's kinda in my whole body. I've found putting pressure on the lower part of my head seems to make it feel less intense. It's not painful just incredibly uncomfortable. I'm also autistic so it just sends me into sensory overload immediately. It's been getting worse and worse. Walking seems to trigger it. Today I spent the whole day in bed and I still experienced it when getting up to use the bathroom and stuff. It's not actually when im walking it's once I've sat back down I feel it. It happens when I'm just sitting aswell but Everytime I walk It does it. I don't know if it's been less today or I've just noticed less. It's really freaking me out because I don't know what it is or how to even really describe it. When I've googled brain zaps it says it only last seconds this goes on for ages. Like this no stop pounding feeling and it's not painful just really uncomfortable. It starts really intense and then eventually settles down a bit. It started only being occasionally. Now it's literally every second of every day and I'm probably making it worse getting upset over it's just such an awful sensation.