Real quick statement and question

Hello ok so i weight 279. Yes i know overweight i have depression and tended to eat and not be active. Something clicked in my head to get up. So i started walking again. About 45 mins (Determination hit). I want to exercise badly but last night i found out im pregnant. I have 3 kids so i get you gain weight. But I'm wondering is its wise to still walk that lenght and i also wanted to know what are good exercises you guys did or do to stay as fit as possible? I was trying to.work on my stomach, Thighs, Glutes, arms, and double chin. For the past few days Ive walked in the heat when its at its highest it feels good to me idk why.