Laura I too have a mum who I believe shows significant BPD traits (not diagnosed). It is not an easy road having a parent who requires/demands constant support... . I agree with
ambi, you have shown incredible resilience in coping with her behaviour.
I am sure you will find this website incredibly useful. There are many members here experiencing the same situation as you.
It's great you have taken such time to post how things have been until now... . it will help others to appreciate how challenging things have been for you.
Congratulations on your recent engagement!

I can imagine the strain your mothers illness puts on your relationship with your man. The tools and lessons here will help you, and as a consequence take pressure off of your partner... .