Making decisions are hard to do. My younger sister is like that, whether she makes a small decision (like choosing what shirt to buy) or big decision like (what course in college to take).
As I read the thread, you are finding it hard to identify the reason why you can't trust yourself on making decisions. I can probably help you by relating your situation with my younger sister's situation.
I think the root of the problem for my young sis for why she cant easily make her own decision is because she grew up looking up to me and my older siblings. We are always the ones who make decisions because we're older than her. Now, she's 20 yrs old and she still doesn't know how to make decisions. For example, she always asks for my choice on clothes that she wants to buy. We clearly have different tastes in clothing that's why I tell her to make her choice herself. Give her an hour and she'd still be standing is the same clueless spot. So I decided for her in the end.
I guess what Im trying to say is, it doesnt matter what you choose. You wont lose anything. Cos you never had those two choices to begin with. and at the end of the day, when you finally chose one of them, then you'll have one.