Guilty about being very irritable at week 34

Since week 33/34, the dreaded heartburn and nausea have made a come back. Not sure if it is the discomfort or hormone but feeling very irritable lately and most of it has been directed at my 3 year old. I know rationally that most of the time she is quite well behaved but I find myself snapping at her (more frequently) when she is not listening / behaving (which I know is normal at her age). I always feel very guilty afterwards for being harsh but just can’t help myself in the moment. I am not sure if it is a pregnancy thing and it will pass? I really hope so, it’s really draining with the constant guilt.