Opening up to parents - advice needed

I'm sorry if this isn't the right place to ask, but I've zero clue where to ask such a thing.

I really don't understand it. Why WHY does it have to be this difficult to do it.

I (27M) lived in another country for the last 6 years and have been visiting home once every 1-2 years or so, which is starting to very negatively affect my (traditionally-raised) mom, who thinks I'm a loser and never bring a girl for them to meet. I'm turning 28 soon, and I completely agree that they should feel anxious that I've never brought (or, at the very least, mentioned) anyone.

Except that this is the very opposite of what's happening.

I have a girlfriend now, who I'm with almost a year. And I really care about that person.

I have had girls in the past. Heck, I've even had sugar mommies in the past and never had any issues meeting people I had romantic interest in.

But - I've never my entire life been able to open up to my parents. Even when I lived at home.

As I'm leaving home soon again, I made my parents coffee this morning , sat them down, and was about to tell them, but I COMPLETELY FROZE UP. I was practicing what I was going to tell them for a week, I was writing reasons down on my notes that if I tell them my mom will finally stop worrying I'm always away and NOT alone. I couldn't do it, and my body just turned against me. I kid you not this anxiety made me feel pain in my kidneys (weird place for physical pain to manifest, but yeah..). I feel like any progress I've made on wanting to open up to them is gone now, and I feel like a POS for literally having my body turn on me and not let me open up my mouth and say it.

I feel this insane burden for knowing I should tell them, but I'm completely unable to do it. I've also been through some shitty periods in my life, but just this fear of opening up to them scares me more than anything.

What the fuck is wrong with me??