ugh help!!!!

Alright I need to know if anyone else has had problems like me. Last month my period was very light 3 days. Usually 5 to 6 days. This month I was 2 days late. Started and it's the 3rd day and it's gone. I've went to the dr. Pregnancy test was negative. I'm no stressed or anything. Haven't even changed my life style. I'm not sure what's going on. Please don't judge me. I'm 23 years old. And my boyfriend and I don't use protection. Not sure if that will help lol.