I would recommend getting a dog.

Hopefully you are not co-dependent or trying to fill a void, you never had fulfilled by parents, with a romantic partner. This is co-dependence explained:

"Dependency: Codependents need other people to like them to feel okay about themselves. They’re afraid of being rejected or abandoned, even if they can function on their own. Others need always to be in a relationship, because they feel depressed or lonely when they’re by themselves for too long. This trait makes it hard for them to end a relationship, even when the relationship is painful or abusive. They end up feeling trapped."

[psychcentral.com]

"I feel so depressed because it feels like my life is going backwards"

Well... That's because your life is indeed going backwards. See you were out hunting and you were coaxed inside under promise of warmth, and what were you given? The cold shoulder...

Actions speak louder then words. It sounds like you need more from the relationship than you are getting (or that your girl is capable of giving). You should not be settling for scraps. I was putting up with a lot of nonsense at the end of my marriage and I finally had to admit that I should not be trying to save my marriage "at all cost" (not worth my self respect and compromising my values). It sounds like it is time for you to move on. Being alone is an adjustment but it is so much better than losing your sense of self worth. There are tons of people in the world....there is a better match for you out there.

It seems to me that all worthwhile relationships operate on the basis of reciprocity. Many relationships begin with unstated reasonable/unreasonable expectations that surface sooner or later and often prove a testing ground that determines whether or not the relationship will continue and move from strength to strength.

Of course, there is the time investment of 3.5 years and like any kind of investment of this nature there is often a reluctance to let go of it and whatever thoughts or beliefs one has formed about it. I think that after 3.5 years all issues of trust should have been resolved

Personally, if I think that it is time for both of you to sit down and do some straight talking with one another and decide where the relationship is headed, if anywhere.

I don’t think the problem lies with you but with her. It sounds as if she doesn’t want to commit, but is keeping you dangling instead of being truthful. After 3 and a half years she should know if she wants to make your relationship permanent or not. You need to have a very frank talk with her and get her to say yes or no to whether you’re staying together as a couple, and that means co-habiting. If she won't give you a straight answer, then I feel you must walk away, no matter how hard it will be for you to do so. There are other women out there who would appreciate your qualities better than she. She has eroded your confidence, that may or may not be deliberate on her part, but no matter, you cannot let it continue or your health will suffer. Your happiness and wellbeing are important, so start thinking about what’s best for you.

Run!!!!

Be careful friend she is using you, run like hell, been there and the worst is yet to come

Well, why can't you be with her when she's busy and help her.. She'd be less busy and you both would be spending time together...

I don't know this woman, but I suspect that if I were to meet her and we had a few heart-to-heart chats over coffee and prosecco I'd very soon discover that she has some trust issues - I'd bet a pound to a penny she's been hurt, probably badly, by another man who said he was a decent man.

I don't doubt for even a moment that you are a genuinely decent man; I've read several of your posts on here and sense that you are. Prove that to her by sticking by her and being there - if she's been hurt, she needs to know you'll do that.

A bad situation to be in.

Diversify.