Bilateral breathing problems

I have been a right side breather for over 50 years. Last year, I tried for a full year to breathe on the left but encountered a lot of problems and I am a patient person when learning something new/different. Here are the problems:When I breathe on the left: I get a headache quickly; also, I get extremely dizzy, and finally, I start seeing spots optically. I also don't swim straight which I am famous for doing and that is because my non-breathing arm is probably traveling to the left. I can breathe on the left for about 10 to 20 strokes before these problems start occurring. Today, after I came home from swim training, I started thinking about why all this is. The one thing I did do was, as I was sitting, was I turned my head to the right and my chin goes beyond my shoulder. I tried this to the left and it wasn't even close to my shoulder. So now I am thinking that muscles/tendons in my neck are not lengthened and flexible when turning it to the left thereby the problems I may be encountering when I try to breathe to the left. So, if anyone has any ideas, or knows of any exercises I could implement to get my neck to turn to the left, let me know. I truly don't think that swimming 19 miles breathing only to the right is the way to go; it may even cause me to abort the swim. Breathing to the left is almost impossible because once my vision starts to go, I get nauseaous. Ideas? Donna