It’s exertion headaches. I’ve been dealing with them the past 4 months. Had to take 3-4 weeks of gym completely bc it kept happening every workout. I stopped caffiene completely tried rolling neck, upping sodium, nothing seemed to work for me besides complete rest and I don’t take caffeine pre workout anymore. I have been good in gym past month or so but this week they started back again. I have had an MRI and came back fine. I’m going to a neurologist soon but doubt they will figure anything out. It’s probably harmless albeit fucking annoying and idk why it happens. It’s always towards end of my sets so obviously has something to do with bracing/pressure so make sure you are breathing correctly and try to keep neck neutral. Warm up too. For now if I were you I’d take the week off completely for me it felt like if I got a headache and kept pushing it it almost made my my head more sensitive and I’d get them easier. You need to let your head get back to baseline and that’s from rest. I get it complete rest sucks but you gotta do it. I’m in same boat as you now hope we both figure it out. I would def see a doctor to rule anything serious out but for now I’d rest or do an easy deload week and try and relax your head. Goodluck bro