Extra blood flow FTM- please help

I've got a question regarding the extra blood flow in our system, since around one week time I'm feeling the blood flowing in my head, hands, sometimes legs and even in my back, sometimes I feel a heart palpitations for a moment and a bit dizzy. But the one that scares me the most is the blood in the head especially when I go to bed or lay down I can feel it all the time. Is that a normal pregnancy thing or should I be worried and go and get checked as soon as possible? I'm a FTM 18 weeks 6 days 

Please I will appreciate all your answers !