I am 16 years old and me and my boyfriend decided to have unprotected sex multiple times 1-2 weeks after my period and I let him "finish" in me 6 different times, and I've been feeling a little off, so I'm wondering could it be possible for me to be pregnant ? And what are the chances ?

You could very well be. I would consider using a pregnancy test ASAP. As well why are you having unprotected sex at the age of 16? You are young and have a full life ahead of you. You should always have protected sex at that age. Get a pregnancy test at your locale drug store and make sure. Keep in mind they are not 100% accurate so you should also see your family doctor. As well you should get tested for and STDs . If you only new the thousands of cases going on in the world you would understand.