I didn't meet my DH until I was 25, nearly 26. I haven't had any one night stands, but had a fair few mid-termish relationships, including some experimentation in my early twenties with girls! So consequently have had a fair few sexual partners. I know it sounds horribly smug, but all those experiences made the mind-blowing factor with DH that much more...mind blowing.
I don't know OP, it's a hard one. I sometimes wish I'd met DH a lot, lot sooner and when I read on here about people marrying their teenage sweetheart, I get a pang of jealousy. I think about all we could have accomplished together, as a couple - getting married earlier, buying a house, having children earlier...
But it what it is. It seems like the human condition to want what we can't have :) Do not beat yourself up for very normal thoughts but just as I can't change renting and having our first child at 32, you can't change this situation either without some drastic - and very unwanted - sacrifices, I'm guessing. It's very normal, very usual and very understandable, I think, for you to be having these thoughts - but unfortunately no amount of people telling you that the grass is not greener is going to satisfy those thoughts. Only really time, and addressing if these needs really do need to be met will :)