Tips (healthy eating & exercise) for first time mummies to be!

Hi ladies, this is my first baby. I'm currently 13 wks + 3 days & I cannot stop eating rubbish food (cravings). My doctor told me I haven't put weight on since I was last weighed around 6 wks which i was so shocked at!! But still, I'm feeling sluggish & unhealthy! It's just so difficult to eat healthy when all I want to eat is rubbish! I never thought it would be this hard😂 Any tips for exercise & healthy eating options?