Normally someone that would have been as involved as you were in Hillel was doing so out of personal motivation and not due to parental peer pressure and I suspect that whatever your religious practice level is has been motivated by personal choice.
The point is that you probably practiced what you did in the past due to involvement in family and friends and continued into adulthood out of a habit which you are now questioning. By not fasting on YK you have crossed a red line in religious Jewish practice and I think you understand this. Its a crisis and there is help available.
I would suggest you speak to someone who can help you navigate the feelings you are having and Aish Hatorah is an extremely reputable institution that helps people in your situation every day. As far as I know its free as well and can be anonymous.
They have a live chat rabbi who can help provide guidance: https://www.aish.com/
Look for the live chat.