Hi OP,
I would look at this response as a good thing and not a negative reaction. I know its very upsetting to hear but you can make changes and so can he and you both can get back on track. I think you should lose weight but not just because of him but for your health, well-being and confidence.
I would advice (money dependent) that you get a personal trainer or start the gym on your own at least. I love the gym and have lost quite a lot of weight from excising so please pm me and I can go over a lot of work out and diet advice which will really do you wonders. First thing is first, join the gym, start cardio, HITT training and some strength training. Go to classes also and see if you can gym it like 4 times a week or 3 times to start yourself off! Try to eat clean and have one cheat day a week (cheat meal more like!).
Set goals such as:
When I have lost 5 pounds I will buy myself some new underwear.
When I have lost a stone, I will buy a dress dress for a night out
When I have lost a dress size, I will change my style
I aim to feel slimmer and buy a new outfit for Valentines Day
I aim to lose X much weight by first dress fitting for wedding
Things like that and do not overly go on to DP about this and say you are doing it for him. Just subtly start making changes to your diet and work out regime and when he notices you wearing sexy underwear and new sexy clothes, he will pick up interest again.
When you talk to him about his text, say It's okay, I asked you for the truth and as hard as it is to hear, I aim to try and make some changes this year to become healthier and happier in my body When you cook meals, cook them as a family so he is eating healthier also and then when he see's you going to the gym, he may tag along.
I think its really important that as a couple you understand the importance of losing weight and staying active and be healthy. Not because of being a size 6 or 8 but because you reduce the risk of heart disease and stuff like that. Also you will be more active and be a much more active mother when your kids get older. It will encourage them to be active and eat healthy.
I hate to say it but some of my bad eating habits were engrained in me from an early age when my parents would take me to McDonalds or buy takeaways.
I wish you both the best of luck.