Yoga and lumbar lordosis

DyneSalcar

Any fitness, yoga, or physical therapy experts here? I have lumbar lordosis, aka an overarched spine and weak lower back and core muscles, which is actually a pretty common side effect of obesity (though it can have other causes).

I have recently restarted doing yoga but can't afford a class. I've had no back pain during practice but I started noticing a few hours after doing Hatha yoga sessions with strength poses, my lower back is sore and fatigued. It's different from the pain I've had from the severe pains I've gotten in the past from the overarch but I want to make sure I'm being safe. Does this sound like pain from doing something wrong or from building my support muscles?

ETA: I try to be especially careful not to overly round spine during forward stretches, and low back tries to overextend when laying flat on my back so I have to adjust floor poses slightly including corpse pose.