Is it normal to be so tired?

Hi, I'm 17 and im 15 weeks pregnant as of yesterday. Lately, i've been so tired after doing the most miniscule activities, that i can hardly do anything. I thought maybe it might be the heat and with me already growing and so forth, but now im not sure. I walk around a little bit and i feel like i haven't slept in years. Is this normal? and if so, is there anything i can do to not be so tired?