Guilt, Shame, Fear re: secrecy

Long story short I met a guy who was married, then I broke up with him a couple of months later because I wanted a proper relationship with him & I couldn’t do that while he was married.  He called a couple of months later to say that they were getting divorced, so we got back together and have been together throughout their divorce.

My mum is an amazing person but can be a very unsafe person to share things with because of her own personal baggage, judgments, etc.
When I met this guy, I was actually living with her & whenever I’d go see him I lied about it because I knew the kind of judgment I’d get from her for so many different reasons.  I simply did not want to share that part of my life with her at all.  At some point, she found out (I have no idea how) that I was involved with a married man in some capacity.  She stopped talking to me for a while and told me I had to leave–totally understandably–so I got my own flat.

I’m feeling a lot of guilt, shame, and fear around:
-having hid my relationship from my mum for years
-not wanting to over-explain and over-share every detail of every part of my decision making process over the past few years so that she understands and isn’t angry with me/judgmental of me
-feeling ashamed that I care this much about what she thinks about my decisions and my choices
-fear around having the conversation where I tell her we’re getting married if we decide to do that
-fear around having to “stand my ground” and not engage when she asks me questions that I don’t have to answer
-fear that she will never respect my decision or simply my right to make this decision and that there will always be tension there
-fear that she will stop talking to me again (this has happened several times with me and with lots of different people as well that she just cuts out for good reason or not–like I said, she has baggage and major trust issues & actually has been betrayed many times so I understand)
-shame and guilt around hiding things from her but ALSO understanding that it was my life, not hers & that I chose to keep it from her for good reason–she’s proven that she is incapable of being understanding in certain situations.
-exhaustion from hiding this part of my life from her for so long.
-fear around what it might mean/what might happen if she really never does choose to accept me/him/this relationship even though she doesn’t like how it started. If I choose to marry this guy, I might be making a decision that she will never accept/move past and never forgive me for.  And I don’t know how I can just say “Hey sorry for lying to you about this very important part of my life for years–can you just forgive me please and move on?  Cheers.”  Really appreciate your help & perspective.