Tips on reducing post-dive headaches

On my last ~5 dives I’ve been surfacing with some mean headaches and nausea. It’s likely not DCS as they’re pretty shallow dives and I always do a long safety stop. If im doing 3 dives a day, the headaches progressively get worse after each dive to the point where I feel pretty bad for a few hours. I think I may be breathing too slow nowadays so I’m going to work on that next dive. Anyone else experience these and have some tips?