You're not being horrible. Not at all.
I do think that your hesitation to continue this relationship, in spite of how much you like him, speaks volumes. You're spending a lot of time trying to convince yourself how great he is for you, how much you "should" want to be with him, how amazing he is, how much he already loves you. You also keep saying it took "a long time" to agree to date him and then "a long time" to introduce him to your kids... and the insinuation there is that he hounded you and hounded you until you said yes. And you never said what "a long time" was. A month? Six months? A year?
Then you dropped the bomb that he's very possessive. I also would be concerned if your children are young and not quite into their teens or younger. I just... I see some red flags with this guy. I'm sure he's picking up on your insecurity about being afraid to be alone without a man.
When you have children, when you're this age, just out of a long term relationship and have never, ever been alone... this is the time that you need to figure out who you are without a man. Concentrate on yourself before jumping into another relationship. You need to gain confidence in who you are as a woman, as a mother, as a friend, as a newly single person so that when you ARE ready for a new relationship (which clearly is not now) you'll know what you want and who you want and will be able to stand up for yourself and your children.
So I'm sure you can guess my advice. Let this relationship go and learn how to be your own woman independent of any man. Learn how to be confident. Figure out who you are. If this man is worth anything at all then he'll understand and he won't push it or put a time limit on your need to grow.