The First Day Of My Last Period Was December 23rd

The first day of my last period was December 23rd and the last day was the 27th -28th or so. I'm every 21 days clockwork. However I'm spotting today. I am also recovering from a uti. I didn't get antibiotics, instead I flushed it with lots of water, vitamin c and water and vinegar and water. I feel unusually sluggish. Just had a normal bowel movement after several days....I'm thinking perhaps very early stages if pregnancy. The last time I had a Uti I was pregnant. ...almost 4 yrs ago.