Breathless, I really need help.

Eva • My husband and I have a son who is 3 (10/5/15) and a daughter who is 1 (11/30/18) and we just found out we are expecting again!
I am a ftm, and I am 12 weeks tomorrow. I am becoming very breathless. I can't walk or stand for more than 15 mins without feeling like I cannot breathe and then I get dizzy and lightheaded. And most times I will throw up. If anyone has any info on this or when it stops please help!!