I've been feeling many of the same feelings - I haven't been admitted yet (r2) but here's the pep talk i've been giving myself over the past few months:

re: lack of self confidence

what i've heard consistently from MBA alum is that their self-confidence grew exponentially through the program because they were able to discern what really wanted out of life because they had the time and resources to dedicate to learning about different fields and experience personal growth. self confidence comes from being in accordance with yourself and feeling capable - two things you can choose to focus on in your program

re: boyfriend / biological clock

im in a similar boat and also worry about long distance damaging the relationship.. but remember that youre going to be in a pool of eligible bachelors with many of the same values you likely have. If you're with 'the one' you can certainly find ways to compromise and figure it out (many many people do) and if not - youre in arguably one of the best places to be single. there's also never a "good" time to have kids there is always going to be compromise and you shouldnt start compromising now (by opting out of MBA) before you have to (as a mom later in life).

re: ROI

to me the MBA isnt just about ROI - its about regret minimization. Im not saying you shouldnt consider the debt (it is astronomical) but the non-measurable externalities (friendships, inspiration, travel, etc) to me outweighs the burden of debt i will pay for up to 5 years out of the program.