Taking levothyroxine when pregnant: side effects anyone?

Hi I’m taking levothyroxine for my under-active thyroid I’m 24+5 weeks pregnant and have been getting really bad headaches and feeling generally crap all the time.. I forgot to take the tablet the other day and the next day I felt way better than I have been feeling and no headaches (which felt so good as I’ve been having them everyday for weeks now) I purposely didn’t take it again and same thing the next day.. so then last night I took the tablet and feel awful again today! Anyone else having symptoms like this?