Thanks for your question, and I am glad that you are seeing someone to help with your weight. There are a few different explanations that can explain your feeling of nearly passing out when your stand up. One of the most common is due to low blood pressure that changes based on your position. These are called orthostatic blood pressure changes, These can be checked readily by your doctor
, and if needed, treatment can be initiated. To check them, your doctor will check your blood pressure and heart rate in different positions (lying, sitting, and standing) and see how much variation there is between each. In most people, the body should be able to compensate for these positional changes quite easily, but some people do not have that ability. This is sometimes caused by medications, and so it is appropriate to speak with your doctor about this symptom as you have recently started some new medications. Other explanations do include low blood sugar, which would be more likely in those with diabetes. Your doctor can also help you with this. Finally, there are a host of other, less likely, possibilities that should be considered as well. Please speak with your doctor about this question.