You also might try a monitor, I have a 7" dual band monitor I clip to my qx7 when I'm at the park so I can still see when people are walking up to me and when I have a headache easier on the eyes

Make sure the goggles fit you properly, if they move about on your face they go in and out of focus, that increases the strain on the eyes - For my old Aomway commanders V1 (designed more for asian faces) I cut some hard foam inserts from cobra motor boxes to fit between the face plate and the foam padding and push them out past the bridge of my nose. 
I also toggle the OSD on and off on the Taranis, (I have the Taranis set up to squwak at me for critical stuff like timers, RC link quality or low Vbat) I found that static OSD images imposed over a dynamic video feed also strained my eyes and were a little disorientating generally increasing that dizzy feeling. I got used to it but I still find the OSD distracting when I fly acro, so generally switch it off, it just fires link / Vbat warnings at me.

If it is motion sickness, Bonine works really well.

When I first tried FPV, it was a bit disorientating but the feeling passed. Of course I'm just hovering around and not doing anything crazy yet.

For me the most important thing is to not move my head. I can stand or sit - It doesn't matter...but I still have situations like that:I have Mobula I fly over my apartament a lot. Sometimes when my wife enters room I fly at that moment and brings something, I want to know what's It is, and instead of yawing mobula, I accidentally move my head which confuses me...soo weard feeling...