Period whilst pregnant ??

Me and my partner have been TTC for 6 months I have a 20 day cycle like clock work!! But this month I was almost a week late for my period but it's different than usual I'm getting really bad cramps on my lower left side headaches constantly thirsty and always hungry but as soon as I eat I want to throw up and very sore soft puffy boobs??? Have taken pregnancy test day of my missed period came back neg any ideas please HELP!!