i am a 27yr old female and my period usually occurs every 6-8 weeks. i am currently on week 4 of my cycle between periods and the day before yesterday i experienced intense cramping similar to my period as well as very light bleeding that has continued into today minus the cramps. this started the day after a big hike (i am not generally very active) and the night before that i had a few drinks. could this be something other than pregnancy?