Anyone else completely out of breath just from walking?

My husband and I try and go on daily walks around the neighbourhood so I’m getting some form of exercise. We just went for one this morning and it was a struggle for me. I felt discomfort in my lower abdomen, I was out of breath a few times and had to take a couple of breaks and then when we got home, I walked up a flight of stairs and got super light headed and thought I was going to pass out. I’m 21 weeks and want to keep walking, but am scared to do so if this is what’s going to happen every time now. I can only imagine how difficult it’ll be when I’m further along...😳