I am using the tocloft package to generate a list of equations I have in my thesis for the table of contents. It builds successfully with the following code:
(By the way, I recommend using \text rather than $$..$$ to escape back to text mode inside the equation, but I don't think that's your problem. Also, I wonder why you don't use \newlistentry instead of \addcontentsline)
I haven't considered using \text and \listentry to be honest. However, I found that the problem can be solved by simply moving the \myequations command outside the equation environment and have it immediately after the equation code.
I think this is because \addtocontentsline uses the equation counter (\theequation) so it might be resetting it or something but just moving it outside the equation block did the trick.