Running a little late...

I am running about a week behind on my period maybe a few days more..( and I have always been regular even since getting off my birth control..) I have taken 3 tests because 1 said there was an error... They have all come back not pregnant... 

I am gaining weight.. My boobs are extremely sensitive I am not craving my normal every day foods, I feel moody and just not my normal self .. 

I would love se other opinions as of to what else could be causing negative tests or am I going crazy or what is going on!!

Thanks everyone!!