OP - firstly, please, please stop talking about yourself in that awful mysoginistic way - 'cock teaser' 'flirt' - you were young and single and could do what you liked, I find it so upsetting to hear you denigrate yourself in that way, even light heartedly - it's so damaging to be critical of yourself and your behaviour like that, and I think you are internalising your boyfriends views of yourself.
Please get some confidence and try to rid yourself of any shame over your own behaviour - and stop letting him make you feel like you have to constantly prove you are worthy of his trust.
I am going to give you the perspective of someone who has really, really suffered from jealousy - me. I had therapy and I sorted out my own issues - nobody could have helped me by changing thier behaviour, no matter how much I tried to control them. I realised it came from my own family dynamics/ what I saw growing up in relationships - my OWN insecurities - not the behaviour of others. Yes of course, I needed to be with a trustworthy person - but you can't make someone be trustworthy, you have to choose a good persono and then back off and trust them.
Telling you off for flirting on the phone with someone in a call centre? dear god woman - stop trying to pander to this controlling crap AT ONCE. I cannot believe women are coming on here telling you to stop flirting with people in call centres.
If you are by nature talkative and friendly - stay that way! If you are chatting with someone in a call centre - how on gods earth is that a threat to your relationship?
You cannot change him - except in one way - stopping all toleration of his jealousy.
He chose to be in a relationship with you knowing who you are. The past is just that, the past.
I tell you from my own perspective, I have only got rid of my jealousy with serious hard work looking at my OWN issues - not trying to control others. I had to make the decision to TRUST my partner, not try to watch him/ stop him doing things I don't like.
Yes, you have to show and demonstrate you are faithful - but he is not entitled to nag/ judge/ call you a flirt for normal human interaction. And you seriously need to get rid of the guilt about your past.
You are young. You were young when you met and he is not entitled to hold your past against you - that is vile and unpleasant.
Me and my partner never - or rarely - talk about the past, it's not relevant to us now. I don't care how he behaved before we met, he doesn't care how I behaved - and believe me, there is a lot of murky crap in my past! I feel so relieved and happy to be with someone who would never, ever make me feel ashamed about my youthful behaviour....I couldn't be with someone who did.
I would recommend that if you are carrying around any shame/ worries about your past - you consider seeing a therapist, it was the best thing I ever did - and I had very similar issues. Have a look at the BACP website, it can be reasonably cheap and you can have short bursts of it rather than years if that's what you want.
You can't change him or alter your behaviour to appease him. Tell him that you are who you are, that he either trusts you or he has to go. I think you'll find that's a far more effective way of working out whether he is the one for you than constantly walking on egg shells.
btw. remember this - his jealousy is his issue, from his past - it's not about you.