but when I do my Kegals the next day I get rectum 'cramps'. And I know it's really important to do the Kegals! Still, the next day I get bad cramps in my back side, really painful. And I am in my 6th month, no chance of ectopic here!

How far along are you?
Call your Dr., follow all the good advice so far and keep on top of it but I say also add some fiber and there could be other reasons as well, just best to rule out the bad ones.
Good luck to you,
Sara H