What Causes Weakness And Nausea With High Blood Sugar Level Post Delivery?

hello. i am 29 year old female. i just gave birth with twins 3 months ago. i was diagnosed with gestational DM and sever preeclampsia. my BP is okay now, but my glucose reading still reads between 120 to 199 2 hours after meal. right now, i feel like throwing up. i feel weak and slightly shaky. i also feel like my pulse is slighly faster than normal. i am wondering what are possible reason/s why i am feeling this. or is this assosiated with DM?