OP
I hope my blunt reply doesn't sting too much, my intent is not to hurt but shake you into reality so that you can start feeling better. My friends lean on me in these situations as I am a no bullshit kind of friend and refuse to prop up false narratives or lie for the sake of feelings.
You appear incredibly defensive and continuously re-explain your situation. You appear to want someone to blame for your losses and your weight. Stop feeling sorry for yourself and giving yourself permission to spiral into self-pity as this is your biggest problem IMO. I'm not trying to be cruel, just honest and to-the-point. I'm not posting to give you false praise or to defend or discredit your partner. We want our partners to be honest right? Or do you prefer a world of "white lies" and false pretenses?
DH and I have a standing agreement to sit each other down to discuss weight (for either of us) if it becomes an issue - the conversations are loving and careful but are HAD... because we owe it to each other - we want to stay happy, healthy, and in love.
But let's be totally honest your issues aren't about your partner. Yes you and he obviously have some issues but to work on those you have to be clear-headed and confident in your worth. You have to set the tone as it appears he is a little tone-deaf but that is a subject for another thread IMO.
Right now for you it is really all about how you feel so let's focus on you. 
Facts:
- Your losses of love are incredibly painful, you need to deal with your feelings and grieve properly. You deserve to enjoy fond memories of your loved ones and not be plagued by overwhelming grief.
- Sex as a connector - can be important but is dangerous if it is the only method of connection/comfort with your partner. Healthy relationships can have dry spells sexually so connecting on other levels is paramount.
- Extra weight does not invalidate you, just makes you unhealthy and unhappy. You deserve to be comfy in your skin and to feel sexy for yourself. You are obese and that's okay, work towards being healthy not being thin.
- Diets DON'T work, changing your diet is a lifestyle change not a temporary fix. Exercise paired with a consistent healthy diet is key to long-term weight management. A treat now and again is fine (I reserve them for menses time) - I just made homemade chocolate custard separated into daily 1/2cup servings to help subdue Aunt Flo.
- A loss of 5lbs in the context of 189lbs is not noticable or notable. I'm 55lbs lighter than you and 2" taller but don't see a difference with 5lbs up or 5lbs down. 1/2lb a day is healthy weight loss so 5lbs in 10 days is right on target. Keep working it and you'll get to where you want to be - be patient with your progress to avoid feeling discouraged.
- Walking is decent exercise but you need to get your heart rate up and sweat so walk swiftly. Try adding in some planks (core strengthening) which will help you with back discomfort and post workout pain. Weight training is better for weight loss than cardio but if you try carrying 2 - 5lb hand weights while walking briskly and pumping your arms you will get some effect from the weights. Once you can handle briskly walking for a considerable distance (2 miles+) while using your hand weights add in some ankle weights and continue as before... at this point you will not only see some results but you will feel stronger and have more endurance.
Last but not least - starving yourself (intentional or not) is unhealthy. Your body will begin to hold on to fat reserves as it will be in starvation mode. You are unlikely to have much or lasting weight loss while starving yourself. The weight loss you do have will likely be muscle loss as the body uses protein reserves after it exhausts gastro contents - it will burn some fat but your body needs protein to function so muscle degradation is a serious concern.
Please love yourself and try to pull yourself out of this spiral. Get to your GP for help eating as you say you are and focus on feeling good about you. Get some MH support - go private if you have to as your life is more important than a few £.
Try this podcast... Nora is funny and open - start at the first episode so you can hear Nora's story of loss. The stories are tear jerkers but allow room for laughter. Her podcasts have helped me through a few losses.
Terrible, thanks for asking
www.ttfa.org/
YOU DESERVE TO LOVE YOURSELF AND YOUR LIFE [hugs]