Bras and stretch marks - questions!

Lisa • Married 5 years to a wonderful man. Son born 26 Jan 15. Expecting another boy in Nov 16 X
I'm 11 weeks and 4 days and have my 12 week scan tomorrow - ekkk!
​I have two burning questions
​1) My bras are a bit small now - when I replace, should I move to non under wired bras or is unwired bras ok for now?
​2) I know people use oils and lotions to try and minimise stretch marks. When should I start doing this? Does it work ? What's the best product?
​Thanks ladies ????