I hear you, as I said I knew in year one it wasn't viable but I so very much wanted it to work.
It will get worse, your resentment will grow, you will feel more trapped while DP is still leading a comfortable life she won't even consider changing. What the PP and I can see is that you are slowly being suffocated because you want to be the nice guy. Perfectly natural reaction to trying to please DP but you already know deep down it isn't working for you, that's why you have asked for help here.
That you cannot see it happening to you just yet is very common, especially as you are working within the relationship but not upon the relationship. Like businesses LTR need planning, strategy and shared goals to succeed. You don't have any from what you have told us you are both just winging it and it never works out well. If you and DP are to stay together, grow together, and find happiness together you need to work upon your relationship so you are happy within your relationship. DP is already happy, she has all she wants and is happy to stagnate, you do not have all you want, your needs and priorities are not considered important. HTH I know but that's the honest truth of it.
The first step of that is finding some headspace to make it work if you want it to work. You need out of the unhappy situation and into a place you can breathe and think straight which you can't do at DPs mums house. If you don't burst that comfort bubble DP is living in, DP has no reason to change and grow.
Then you and DP can work on your relationship, give each other time and space to miss each other and to re-evaluate your priorities. If they are still mismatched then they will not align so break it off for both your sakes. If priorities do match then try again but with your own space and your own time to just be yourselves so you can be the best partner you can be to the person you love.
Bit of a trite quote but has truth to it, this is attributed to Albert Einstein but it is relevant for you and your situation
'Insanity is doing the same thing over and over again and expecting different results.'
Make a change, you might be pleasantly surprised or at least much better off than you are now. Something has to change though, just hoping won't make it happen.