Congratulations! Thank you for sharing your experience, it's a great reminder that everyone should be reflecting on their practice and talking with others, and that there's nothing wrong with a question - in fact, there's everything right with them!
Lots of great points already made, I completely agree that you should be proud to have your self-awareness and strength of character to challenge yourself to develop, I imagine some people never learn this.
One practical technique that's helped me is to visualise and run through possible scenarios in advance - and practice out loud - which'll likely feel strange! As already mentioned, a journal could help you reflect on a particular situation and work through how you could have approached things differently. Even better to then put what you've learnt into practice...
You've mentioned that your confidence with other people holds you back, perhaps you could practice stepping outside your comfort zone in less challenging situations - such as (safely) starting a conversation with a stranger? Or in a supportive environment such as becoming part of the Care Makers network?!
You're not alone!
I wonder if you already know the answer to this - but don't want to know it?
As one of the commenters above says, yes - it's wrong to ask them out whilst you're still at the placement. Your mentor's in an important position of authority for you at the moment, which needs to be respected for ethical and professional reasons.
I'd hope that your mentor is equally respectful of these boundaries - and would appreciate you waiting until you've completed the placement!