I can’t even do a 20 min slow walk

I’m 5w1d, today felt fine so went to the gym to get a 30 min walk done. It was the first time since I knew I was preg. I walked casually and didn’t do any speed. After only 20 min, I couldn’t catch up with my breath, started to feel dizzy and back pain... I slowed down immediately, thought I’ll adjust myself and even slower make it to 30 min. But nope, by 27 min I had to stop and lean on the wall rest... then I walked to a couch to rest... when I walked to my car, I felt obviously dragging. I started to feel nauseous on way back, thank god my house is very close, plus the tiredness that I had to hold my body with my right arm when driving. I know I would get tired. But to this level makes me feel bad about myself. I felt so embarrassed when I had to rest against the wall on the track... I feel my body betrayed me and don’t know how to view myself anymore