I had over 50 extremely successful, problem free warm water dives logged as of a few years ago when I attempted my first cold water boat dive in Canada. No one briefed us on cold water diving specifically. We were properly suited up for the temp. When I hit the water I immediately felt that I was having trouble breathing. Thought my suit might be too tight. Unzipped a bit, relaxed and tried to catch my breath. Finally I felt I was ok and we descended to 90+ft. Suddenly I felt I could not breathe again. I motioned to my buddy and we slowly ascended. I was very upset and did not attempt another dive there. Then I was told that it is your body's natural response to catch your breath and not exhale completely when you hit cold water. Since then I have done dives in warm Mexican water just fine. No problems, like usual. A few months ago I attempted a shore dive in Sydney, Australia where the water was chilly but not near as cold as Canada. I remembered the advice I was given after my first cold water fiasco so I felt I was prepared to make sure I was breathing properly. Sure enough as soon as I entered the water I started having trouble breathing again. I consciously made sure I was exhaling completely and trying to relax myself. I felt like I was going to pass out or throw up. And this was before I was even completely in the water! I had to get out of the water and did not dive. Immediately I got a migraine. I am very worried that I have lost my "mojo". I hate to make anyone wait so I know I rush myself when I should not. I have been thinking of going back to the pool or a local lake where I can take all the time I need to get myself underwater and breathing like I should. Has anyone else had something like this happen? Any advice or suggestions? I own my own equipment and we have it serviced annually. My husband is rescue certified and is always my buddy. Other than these 2 incidents every dive has been great! Even cenotes, whale sharks, sea lions, currents and big waves. What the heck is the matter with me and how can I fix it?