Weight loss devastation

Around 6 months ago I had lost nearly a 6th of my body weight bringing me down to almost double digits (102kgs) with a combination of healthy eating, exercise and duromine. Then I got sick and had to have prednisolone and it all went out the window. I couldn't exercise and there was no point staying on the duromine when I couldn't exercise. I put almost all the weight back on 😢
Ever since then I have been trying to lose it, I walk around the block, nothing like the gym workouts I had before. I eat healthy still, full plate of veggies with a little meat but I haven't gone back on duromine because I can't afford it.
Flash forward to the last few days and I've had a specialist tell me I need to lose weight to help my asthma (yes I'm well aware how much this can help) and I need to go see my gp for duromine again and consider surgery. I was devastated, firstly the medication he has put me on costs over $150 a month let alone adding the cost of duromine and secondly I don't want surgery, I know I can get down to a healthy weight I'm just struggling so bad. My partner and step daughter have amazing metabolisms and can honestly eat whatever they want and not gain weight, I just have to look at something naughty and there's 5kgs! They don't understand how hard it is for me to lose weight.
I can't afford a gym membership, walking around the block has proven to do nothing but exacerbate my asthma in the past and I'm just so lost about what I can do. I've seen a dietitian and she has helped so much but short of adding extra costs I don't see how I can lose this weight again