Hello to all i am a newbie here i hope anyone can advice or enlighten me im really confuse

on what to do with my situation.
I have a brit fiance and were together for more than two years now and hes been visiting me many times, we are so much inlove and happy with each other. Now my probelm is this, i have a past which i did not told him, because its one part of my life where i want to forget it and move on and have a fresh start. Its all about i applied a fincee visa before but to a different country not uk, it was denied because there was a foul on the part of the guy and not totally my fault. And now i am very worried because my fiance decided that we will apply for a fiancee visa this year in fact he wants us to sort out the papers as soon as we can so we can be together forever which we both really want to happen.
Here are my questions:
1. i have no plans of not telling the truth to the british embassy i will tell them the truth, but will it affect my application? because of my history?
2. do u think we have a big chance of getting a visa? no problem with the papers and proofs because we have it all.
3. if i dont tell the british embassy that i applied a visa to another country and was denied, will they find out?
4. and lastly, if i will tell the british embassy all the truth and my fiance did not know about it, will the embassy contact my fiance and disscus with him about it?
oh god i have so much questions i hope u can bear with me, i need your advice and opinions. i am really scared of telling my fiance about my past application because i know him too well now, he will really get mad at me i cannot bear it, it scares me that he will change towards me if i tell him. some say that your past is not a big deal to westerners i hope this is true

pls dont ask me why i didnt told him from the start coz i still blame myslef for it

everyone has a right to have a fresh start.