What Could Missed Periods And Painful Nipples With Negative Result In HPT Indicate?

Hi, I'm a 23 year old female and i haven't had my period since october 25- october 29. I was suppose to get it november 28th but it never started. i've periodically gotten cramps but no period. i already did several at home pregancy tests ranging from cheap to expensive and all say not pregant. i've gotten a little bit of weight on me but that could have happened anytime since i am always hungry. i do all kinds of meditation and relaxation techeques and still no period. just today i pinched my nipples and they hurt which is unusual for me. thyroid issues run in my family and i've lost two members to different cancers. i am on ranitide for stomach issues and 50mg amatripaline for sleeping issues i've had for a while.