Irregular

Hi, I know this might be TMI but I’m curious. About 2 or 3 moths ago I had intercourse and he ejaculated inside of me. I had the symptoms of early pregnancy but when I took a pregnancy test it was negative. So when my period came it was very light I normally have to wear a tampon throughout the day but that month I didn’t because it wasn’t heavy. So the next month my period came two days early and it wasn’t as heavy as it normally would be either, and this past month it came 4 days earlier than it normally does it wasn’t as heavy either. I wore a tampon maybe two days and when I went to change my tampons it was was hardly nothing on it. What’s going on? Did this happen to anyone before? I know my mom said she didn’t know she was pregnant with me because she had periods but is this normal? I’ve never had and irregular period before.