Hypothyroidism is a major cause of
weight gain/inability to lose, and often accompanies PCOS and
insulin resistance. The tests you need are Free T3, Free T4 and TSH. You might also ask for thyroid antibody testing to determine whether you have Hashimoto's Thyroiditis.
I, too, have insulin resistance and I take digestive enzymes because I don't absorb a lot of nutrients; the digestive enzymes do nothing to help me lose weight. I also have Hashimoto's/hypothyroidism.