Ok so just about a year in between the first post and update. If you're still in the same relationship it's quite possible your partner is basically ok with it ... there are other possibilities but that's one of them.
As someone who has been in a similar situation, though not for quite as long, it was basically down to anxiety and resolved in time. Partly this happened by accepting that I was basically useless at penetrative sex. This was a painful process but at the time undeniable. From that point onward the stress and pressure reduced and in time the PE just went away, more or less. It wasn't about control or developing techniques or anything, just basic relaxation.
If things are really as described then it's worth giving yourself and your fiancée a break. You can't know she must be freaking out about spending her life having awful sex with you unless she's given you some indication that's what she feels. Maybe she's ok with you as you are. No point always apologising - if you've been together over a year she'll know by now you're not doing it on purpose. You can still give and receive pleasure if you stop fixating on things you can't do at the moment.