She thinks we're moving too fast, changed the pace completely?

[Cerby]

I'll keep it to a brief summary

I started dating a this girl mid January, she had just come out of a pretty bad relationship the month before, and was hesitant to date me originally, but after going out on a couple casual dates she decided to give it a try.

Things started out amazingly well, the first two weeks were great, fun hang outs, good dates, but no physical movement (she stated she wanted to go slow before we started dating). After those couple of weeks, we had some late nights out and she slept over a few times, a couple of times I crashed at her place (but we didn't have sex).
**note, she has never waited more than a week to have sex with anyone in the past, so I'm 3 weeks past that, red flag?

She has been very physically standoffish since the beginning, allowing me only to get her shirt off, kiss, nothing beyond that. A few nights ago I asked her if she would talk to me about having sex (we had been dating for a month now) and she said that she still wanted to take it slow and wasn't ready, that everytime she sleeps with someone early in a relationship it goes badly.

We had a brief talk three nights ago about things, and she said she still felt it was going too fast, so there would be no more late night sleepovers until she felt ready to make that step. I asked if I was just an emotional rebound, and she stated firmly that I was not and she really did want to date me.

So we changed the pace completely, she is still very affectionate when we hang out, and its still a lot of fun, but she also seems to be much more on guard from me making moves right now, making sure I can get no more than a quick kiss in here or there, ensures that each night ends at a proper time so no one will sleep in the others bed. My problem is that the change of pace has left me uneasy, almost like she's backed off considerably.

We are both in ours 20s and have both had multiple serious relationships.
Am I screwed or is she just resetting things so that she feels more comfortable?