So, I Had A Period That Lasted 3 Days, A

So, I had a period that lasted 3 days, a little heavier than normal, when normaly it lasts for 7 days. Then it just stopped... 4 days later, I start spotting, but not enough for a panty liner..only a few watery drops of blood. Is this implantation bleeding? Should I worry? I'm also 19 years old.