Exhaustion while pregnant

I am a stay at home mom with a 2yo. I am currently 7 weeks pregnant and absolutely exhausted. Every time I stand up I get dizzy and everything goes black for a moment then I just feel completely out of it. Between that and just being so extremely exhausted I feel I am not able to give my 2yo all the attention she deserves before becoming a big sis. Any suggestions on how to fight the exhaustion would be very appreciated.