I can't help you any, but I can say that I can relate at least somewhat.
I fell off of a horse in March of my Freshman year at college in 2009 and I have been hitting my head ever since. I have hit my head noticeably about 13 times and as you say each time different symptoms become more prominent or dominate. It was not until my 6th or 9th (I hit my head 4 times in one day ) that the nausea really came on and that was in January of 2011 (I think). But each concussion since that time has had a different effect. With that one in Jan '11 I was nauseated for 5 months and then went back to the just normal headaches. With the last couple that I have had I have been so sick for about a week that I can barely leave my bed and can't swallow any food during that week (good news is that I lose a little weight ). With the last one I got, my ability to follow a coherent story and my ability to focus have been so hurt.
Anyways, need to go to bed.
Just wanted to say, we need to avoid any more head hitting, because it is hitting us too hard (pun intended)
Good Luck!