I’m sorry @georgiexoxi posted before reading all of your updates,, which will hopefully teach me a lesson.
I can see that you were concerned about the trip, taking measures to reduce chub rub etc.
I wonder if you shared any of your concerns with him before hand? It’s ok some posters saying that you were obese beforehand and he should have realised that before but some men —looking at you DH— can be very obtuse and literally need things spelling out to them.
So in your situation, if I hadn’t have said “I’m really looking forward to the holiday but it’s going to be hot and hilly and sometimes I might just need a bit of a sit down and a cool drink. You can join me or go off exploring”, it literally wouldn’t occur to him that I couldn’t do everything planned.
So maybe communication is something to look at improving, on both sides, if you do decide to stay.
And I’m also sorry about suggesting running. It can be useful but I hadn’t realised your BMI when I suggested this.
Totally agree that you need to see your GP about becoming more fit. Losing weight is up to you but if it was me, I’d be trying to up my fitness and stamina first.
And I do get that your DP was disappointed but that doesn’t excuse him for being a dick.
He could have suggested that you had a drink whilst he walked and then took a taxi to meet him or compromised and both gone in a taxi. It doesn’t sound like compromise is his strong point though?
And sulking in the evening is a big red flag 🚩
I think you know that’s wrong of him and worrying behaviour and that’s why you you’ve posted.
Making comments about what you eat and how much isn’t great either. I get that he’s worried, you’ve had a big step up in weight since getting with him, I think you’re averaging a stone a year since you met? He might be worried about you but criticising you and what you eat won’t help you to become more healthy or feel better about yourself as you probably know already.
I think there is a bit of a weird seam through the thread where people are saying things like they never eat cake.
I’m around your height and score in the healthy area for BMI and I can assure you that I do regularly eat cake, your future does not have to be one of austerity. My DF always said “everything in moderation” so I eat cake and chocolate too 
Whether you decide to stay with him or not, I’d think about how you want future to be.
I’m sure you have things you want to do and having the strength and stamina to do those things will be good for you. Having someone with you who doesn’t compromise and sulks might be even better?
I hope you do see the GP and start to make changes, for yourself though, not for your DP and use this experience as a step towards a better future 