Hi OP,
I totally get where you are coming from. I suffered from an eating disorder for 10 years before becoming pregnant and I found pregnancy a real struggle at first. I was weighing myself every day and watching what I ate for the first few months.
For me, (before pregnancy) my eating disorder was about control and I used it as a coping mechanism. When I felt like things weren't going so well for me, my focus was the number on the scales, the number of calories I consumed. I'd eat too few calories, then end up binging and feeling uncontrollable guilt, often making myself sick afterwards and hitting the gym hard.
At the start of pregnancy, things definitely seemed far beyond anything that I could control. I needed to eat to not feel so nauseous, so from the word go, I had lost control of what I ate, my body was changing, etc. I focussed on that, but in reality, I think that I was finding my whole life changing was the culprit for my feelings. I was about to become a mum. I was growing a new life- one that would be wholly dependant on me. I had to think about others for a change and stop being selfish. Despite being in my 30s, I still had a sort of child-like mentality and I knew that I needed to grow up, but a part of me was wanting to be the carefree person that I was before pregnancy. In addition to the eating disorder, I also used to use alcohol to numb myself, which stopped as soon as I got pregnant, so I had lost another unhealthy coping mechanism. I started weighing every day, tried to restrict my intake, etc. There were many times that I felt guilty. Despite this, I was determined not to make myself sick and try to be healthy for the baby, but it was a daily struggle...
I referred myself to the mental health team as I knew that I needed to change my mindset. Putting on weight was hard, but I knew that if I harmed my baby, I'd never forgive myself.
I can't tell you exactly when the turning point for me was, but I started weighing myself less often and stopped counting calories. I'd get my DH to cook for me or go out to eat, as that way I had no control over how the food was prepared (if I prepared it, there would be no oil, I'd pile my plate with veg to make it look full of volume, but low calorie, etc) once I started letting go of the control and eating intuitively, I started to feel more comfortable in myself. For exercise I'd walk with DH or go to pregnancy yoga, but nothing strenuous and if I was tired, I'd have a day of rest. I also started doing a lot more self care. I booked myself in at the hairdresser's, got weekly/fortnightly massages, did face packs and long baths, etc, plus I did hypnobirthing to help calm my mind and build confidence in myself ready for becoming a mum.
I now consider myself recovered from the eating disorder and I can't believe that after 10 years, I can say that. I may relapse once baby is here, but I'm honestly so much more calm and comfortable within myself. My mental health has never been better and people comment on how much healthier I look.
Wishing you all the best, you've done the first step of recognising that you have a problem and have reached out to the midwife and Mumsnet community for help and advice. Take it one day at a time and try to be kind to yourself. You're growing a human being and that takes it's toll, it's obviously had an impact on your mental health.