I'm in my forties and married, but I work with people who are in their 20s and early 30s and I'm absolutely horrified when I hear all the strange and stupid dating 'rules' that are fashionable at the moment.
One young woman was telling me how you're supposed to tell whoever you're dating if you're still in contact with your ex (even as friends) - and, in turn, if anyone you're dating is in contact with their ex, apparently that's an instantly dumpable offence. She's still in the same peripheral friend group as her ex and she was agonising about how and when she should tell this to the guy she's been dating. It was their third date!
There seems to be a trend towards this sort of over sharing confessional as a proxy for transparency, trust and therefore 'dateworthyness'.
Our millennial ideas that how many people you've slept with is no one else's business, are very old fashioned. Now, it seems that the ultimate ideal is that you're a virgin who's never dated before. Hmm that old chestnut... Some things never change.
In short, that can all fuck off right into the bin.
OP your boyfriend sounds like a sulky, controlling baby. He can get in the bin too. He has no right to make you feel bad for sleeping with people before you even knew he existed. Is he a bit thick? I'd dump him for that alone.
If you have had bad sexual experiences where you've felt used or coerced, then that is a separate issue and I'm sorry you've been through that. Any misplaced guilt or shame you're feeling about that is being weaponised by your boyfriend to give him power over you and make it all about his stupid hurt man feelings. Tell him to fuck off and then get some counselling for yourself love.