Honey, they've been controlling you all this time because you've ALLOWED it.

You can't put all the blame on them -- if you had nipped it in the bud much earlier, you wouldn't have this trouble now.

I'm so sorry you're dealing with this. Are you an only child? It sure sounds like it.
You're just going to have to REMIND them that you're over 20 yrs old, and you are an ADULT and LEGALLY able to make your own decisions and responsible for any decisions that you DO make. So you know that if you make any big mistakes, you'll have to face the consequences -- and I'm sure you've thought about that and mulled that over in your mind.

And I'm also sure that you won't expect to run to your parents to bail you out of any big mistakes that you might make -- but no one expects you to make these mistakes. You have a great job and HOPEFULLY even if it doesn't work out with your bf, you'll STILL be able to make the house payments. I hope you've thought about that as well.
Just gently tell them you're an adult -- while you love them, they CANNOT continue to run your life anymore. They CANNOT continue to tell you what to do all the time, as you NEED and WANT to live your own life as you see fit. It's only fair and it's only RIGHT. So you would appreciate it if they would just ALLOW you to make your own mistakes and/or your own decisions and you'd like them to "back off." And reiterate that you love them, and don't want this to become an issue between you but you've GOT to live your own life.
They SHOULD be able to understand, if they look at this as adults and not pampering parents.

It's time they let you grow up like a normal woman!
I wish you the very best. You have a great head on your shoulders, and it sounds like they did a good job. So i don't think they have anything to worry about.

God bless and please take care! Hugs, Lee