What Causes Fatigue, Frequent Urination And Stomach Bloating While UPT Is Negative?

hi, I am very confused at the moment. me and my partner have decided we are ready to start a family and had all are checks upto date. this month my period was 1 week late and extremly light in comparisson to my usual regular heavy flow. it was also very light pink and watery in colour and wasnothing much lasting 2 1/2 days. i had many symptoms, fatigue, urinating alot, tierd, very bloated and extremly tender breasts and sore nipples. i have done 5 tests since and all say negtive what do you think this could be?