I dont know what to expect?

i just found out a few days ago that im pregnant, it was unplanned and very unexpected, im 20 years old and i believe im about 1 month in to this, im very worried about stretch marks, what is the best way to make sure i get little to no stretch marks during pregnancy? and also, i was wondering how big my are going to get? I have 34 DD right now, and im worried that on top of getting pregnant my will also be destroyed along with other things..., I feel like im a terrible person because im worried about this but im only 20 years old, im not ready to lose my looks yet...