Just do what you can and don't pressure yourself to go past your limit. I'm 6 weeks out and walk 1.5miles a day. I was hoping I'd be back to my regular 3miles a day by now, but I've blacked out a couple of times. Yesterday I added an additional 500 steps to my walk and got dizzy on my way home :/
Your diet is the biggest driver of weight loss. Exercise helps, but it's not critical, so if you're struggling then take it slow. Anything is better than no activity at all.