Opinions please ,47 y old

So , after no sex for sometimes I have had sex many times with this new guy. Totally nauseous super tired vomiting almost I thought I was pregnant and then suddenly got heavy periods. ( my periods normally were easy ) , my two periods after being sexually active with this guy were heavy and then one came mid cycle shorter . What was this about? I even took pregnancy test and nothing …is this pre menopause ? why did this happen after sex with this guy . Such puzzle … the assumed “mid cycle period “seems like my period came early and now it seems it adjusted into normal period cycle…

It never happened before. I did have lots of stress too