Long Story Short; Can't break through her resistance.

I'm been having this problem (yes it's specific to a girl, but I'd say it's quite a generic problem, so I hope the advice given will be relevant to many similar situations.)

First Date:

Escalated slowly, drank, ended up at her house, made-out, slept over, but basically nothing else happend. The time period of being awake at her place was probably about 3 hours, so that's a lot of making out, without escalation, and I did push for more.

Second Date (probably 2 month gap between the dates, for sensible reasons, out of country, exam period etc.)

Same story basically, ended up at her place, slept over, but it didn't get to taking clothes off, she was always stopping when I went to touch more intimate areas (tits/pubic region)

Basically I'm looking for advice as to what I should be doing to escalate this sexually, she's obviously into me, but won't have sex. Is it just a matter of more dates?

Thanks any criticism/advice appreciated.