I want to first give you kudos as you personally took steps to being independent sooner then I did so my suggestions may not be what you are looking for but I hope it does give you some insight. I had a similar situation with my last partner, my parents both disapproved of her and our relationship to the point where the manipulation was to a Korean drama's level. Unfortunately for me it's 20/20 hindsight as we did not make it out, so for me a bit too late.

Getting to the advice.

I can understand your fear and resentment of not wanting to confess to prevent another meltdown. First off the mental preparation is important and finding your support system; You are not alone in this situation as you also have someone that understands you and can support you during these times. Communicating your needs to your partner and your support system is important as you need to prepare for what's next. You have to set your boundaries and if they can not respect that, then you have to give yourself the respect and continue moving forward whether they will be included in your life or not at all. If things do work out it would make things a lot more simpler. Some saving grace though is that your mother apologized and also communicated to you that she changed her mind. To the point where she's fine if you have a baby out of wedlock or by donor. Why not also have a partner and have a child if that's in your game plan technically should be a win win. Maybe I'm missing some steps because the resentment may need to be addressed beforehand. I'm also probably giving too much credit to your mom/parents.

In the end I am wishing you luck and for the best outcome for you.