I am so sorry that you have run into this problem and I can understand why you want advice now. As a forum we cannot provide you with a lot unless another person should come along that has experienced the same problem.
Atrial Septal Aneurysm (ASM) treatment depends on the type of ASM you have. This can be treated with a blood thinner like aspirin. However, being pregnant may change your treatment options. You should discuss this with your OB and cardiologist.
I am glad to know you are already booked to see a specialist in this field.
Try not to Google and know that if you feel something is not quite right - seek emergency. I know it is hard not to worry but sometimes keeping busy with out plans helps take your mind off your worries.
and Heart/Cardiovascular Disease. "She Stood in the Storm & When the Wind Did Not Blow Her Away, She Adjusted Her Sails."