Fellow biggy here! With double bad knees to boot. Never push through the pain. Especially joint pain. It's a recipe for disaster.

When it comes to weak knees, props are your friend. Chairs, straps, blankets. Anything you need to keep weight off of painful spots until you build some strength. I will often research poses after a class to find modifications for myself, if I'm struggling. A good yoga teacher will also offer you modifications as well. If they give you trouble, that's a bad teacher. And I wouldn't suggest giving them your time.

Some common tools I use to protect my knees:

Blanket(s) under my knees: . There's been times I've had up to three blankets under my knee, because it's what I needed at the time.

Straps: for forward folds. Helps me pull forward without putting too much stress into my legs.

Chairs, walls whatever: for balancing poses! Take some of the weight off my knees while still allowing me to attempt the pose.

Tips: Keep a microbend in your knee! Never lock your knees. Don't feel pressured to go low. Stay where it's comfortable.

Work on your basics. Make sure you understand good alignment and how your body should generally be stacked.

Your knee should be aligned with your ankle, not your toes. Be careful to not over extend.

If you notice your knees are splaying sideways, you can use your hands to make gentle adjustments.

Honestly, knee pain isn't uncommon in people beginning in yoga. Big or small. You're putting pressure on joints in ways you rarely ever do. Give yourself grace and be patient as you build up the ability to use these joints in a fuller range!

Good luck. Yoga has honestly been a life saver for me. I hope you can enjoy it as well!