You need to give yourself grace. You are only 4 months postpartum. To loose the weight you need to be in the right head space or it will feel like an extra chore.
I gained 3.5 stone in my pregnancy. I gained so much at the end due to sciatica. When I was 4 months postpartum I knew I wanted to start loosing the weight.
I joined a mum and baby fitness class once a week. I walked. EVERYWHERE! I was aiming for atleast 10,000 steps everyday. I was eating healthy meals. I needed them to be easy. So I would opt for veg, rice, chicken ect. I cut out bread and anything with too much starch. I was snacking on fruit and having smaller portions. I wouldn't eat after 6-7pm. Weekends I would enjoy myself. I would eat chocolate, ice cream, pizza.
I am breastfeeding my baby and the one thing i dont have this time which I had terribly with my first is hunger. Thats why I think I found this easier.
My sister is now on her weightless journey. 6 months postpartum and it is so much harder for her because she has that hunger but she is walking alot and doing incredibly well. It is different for everyone. So dont compare your journey to anyone else's. I found it so easy to loose weight after my first. I didnt think about it but the weight just fell off and I was always hungry for chocolate! This time ive been doing everything well but its harder and taking longer.
I am now 10 months post partum and finally just under my pre-pregnancy weight and I am so proud of myself.
The most important thing is do not let this take over from enjoying your baby. Your body has just done something amazing, so be proud of that.