Not progressing fast enough

My(male 30s) going on 3 years relationship with my girlfriend has not developed a deep connection like a want. I've talked to her about this since the 1 year anniversary. I think she is too closed off for me or actually might not even know herself well enough.

I care about her so I'm really hesitant to break up. I don't want to mistakenly break up, but I want a deep relationship and I want to get married soon.

Any thoughts?