Wow, I could've written this exact same thing a few months ago - I too was 19 and had never been anywhere at all with a guy and had just started texting/seeing someone.
Like you the thought of doing anything at all with him really scared me - even the thought of kissing, and I was genuinely scared of having sex with him, even though he was lovely and I really liked him.
I think it's pretty normal, and nothing to worry about. Everyone develops sexually/physically etc at different rates, and the more you get used to being with him and being yourself with him, the easier it'll get to do those things.
I can suggest what I did with my now boyfriend - I explained that I'd never had a boyfriend before and that I needed to adjust to being in a relationship etc etc, and reassured him that I did really like him etc.
Over time my attraction to him grew and I became more confident...kisses turned out to be damn awesome and in no way scary (it really is true that it kinda just 'happens' - I was always convinced it needed a special technique and that I wouldn't know how!), and well, I won't lie, sex initially freaked me out a little, but my boyfriend was lovely and took things at my pace.
And as a reassuring note, I now can't keep my hands off him lol...no worries whatsoever with intimacy and all that...just a matter of getting used to it over time