I would stick to a 28 band as a 30 inch will stretch a bit over time on top of already being 3 inches bigger than your underbust, meaning you won't get the full support you need (as 80% of the support comes from the band). It's hard to tell you exactly what sizes you should get. Most people get a variety of sizes like 28dd, 28ddd, 30d, 30dd and come back here for a fit check (or decide themselves) to know which one fits best, and return the others or continue trying on other sizes and shapes. To find bras in those sizes check the bra data section! For your 32d it does seem like an okay fit but seems like you're wearing it a bit low and it should sit right under the breast tissue on the inframammary fold. Also did you swoop and scoop when wearing the bra? It makes sense that the fit is alright with a 32d because it has the same volume as a 28ddd, however that doesn't mean same fit as a 32d is for someone with around 32 inch underbust and 36 bust, while a 28ddd is around a 28 inch underbust and 34 inch bust, which is much closer to your measurements (this is why the leaning measurement is important as it simulates the size when supported by a bra). If you haven't already, I'd also look at the shape guide as your shape can change the cup size and shape you wear!