Re: what is going on with me?
Good Morning, Paul -
A splint can cause your bite to open up and often that is the planned intention of the device.
There are different kinds of splints which are designed for different purposes. Some are used merely to protect your teeth from grinding. Some add a little thickness to keep your teeth apart and relax the jaw and/or allow movement of a displaced disc. Some are repositioning splints which move the jaw down and forward to a more functional position.
Make sure your doctor tells you the intention of the splint he has made for you and whether or not it can cause permanent jaw movement.
In my daughter's case, she started with a simple splint, but eventually was given a repositioning splint. We knew that by using that splint, she would need work to close the resulting open bite. But, on the plus side, she has been free from TMJD symptoms for a year and a half and her bite has closed through orthodontia.
Paul, do a search on this message board on "open bites" to find others who have had the same problem.