Too early for signs?

I just recently got back on the pill starting August 19th. My husband and I had unprotected sex two days later. I am now feeling some signs of pregnancy at about 3.5 weeks. Is that too early? I’m been feeling very sick at night, no appetite, and today I just got some lite bleeding, and slight cramping and I’m not supposed to get my period until another 4-5 days. Is it possible that I am pregnant? I don’t usually get my period early. It’s always on time and it’s not usually this lite.

UPDATE: took a test just now... it was negative. Could it just be too early? And my spotting is gone. Is it possible it was implantation bleeding?