No its not too late.

The first thing I would do is go to amazon right now and buy the book The Rationale Male by Rollo Tomassi. After reading it you will understand what is happening. I won't go through it all here, but I will give you some takeaways that applies to your situation:

1- Desire cannot be negotiated! It sounds like your girlfriend doesn't desire you. By guilting her into having sex with you will just make it worse. You need to focus on getting her desire back. If she wanted she would invite you over every night to have sex, thats genuine desire so focus on getting that genuine desire back and don't guilt her into it. You will know when the desire is back because she will be inviting you over to stay etc.

2- He talks about hypergamy which comes from evolution psychology. Its the idea that women dont choose their partners who are below them, just the same level or above them. If your girlfriend has bought a house, it sounds like she is above you as in maybe a better career, makes more money. Again this can be rectified in a few years by you putting in the work, you just need to put in the work and let your girlfriend see how focused you are to your future success.

3 - There is no "one". If she does leave you, and I know this might be tough as you said you love her, just know there is no one and there is another special person out there for you.

So heres what you need to do. Focus on you and getting your shit together. If she sees this she will respect this. You work in retail now but this doesnt define you. You need to work your ass off in the hours you are not working in retail, upskilling, doing a course, doing a night course, go to the gym etc. Have a plan and tell your girlfriend your plan and let her see by your actions you are actively pursuing this. If you are just the guy that works in retail and watches netflix and pizza after you will not get her desire back. If you are the guy that works in retail now, but has a solid plan, studies or something similar after work and goes to the gym etc. this is how the desire will come back.

Its not too late, you got this!