Wagtail
Horse servant
Dear lord anyone would think the OP were on the verge of starring in an episode of 'My 600lb life'! Calm down dears, it's just some excess weight. By a horse, or a pony, there's a fair few that would carry you happily all day long. Alternatively, lose some weight and have the pick of the market.
Calm down? I don't understand why you think people are not being calm. The OP asked a straight question because she obviously wanted honest replies. I don't see one person being anything other than calm.
OP, at the moment you probably need a horse that is a little bigger than what you really want. So you need to be realistic. You could buy a horse that would suit your needs right now, and then lose some weight and regret not having the horse you really want. That would be a great shame. On the other hand, most of us know that losing weight is not easy. And if you are to keep the weight off, then it is a lifestyle change for life. I have had to diet in order to be light enough to back my tiny WB mare. I cannot eat very much at all or I will pile the weight back on. It's depressing because I know that is it for life. No takeaways, cakes, sweets (unless I starve myself the following day). It is HARD. So your other option is to lose some weight and then buy the horse you REALLY want. But unless you are confident you can keep the weight off, you may end up having to sell it or keep it as a pet. Only you know how likely you are to A) lose the weight, and B) keep it off. It's not easy. Good luck.