Honestly I think you're being a little paranoid. Unless there was semen on the condom when you put it back on then there was no way for sperm to enter her vagina. While condoms aren't 100% effective, they are still EXTREMELY effective at preventing a pregnancy. So no worries unless a condom breaks or tears.
If you are really concerned, maybe ask if she might consider birth control. You should definitely still use condoms (no way of knowing if she's taking them on the dot every day and some things like antibiotics can make them ineffective and they aren't 100% effective either) but it would be double protection against an unwanted baby. And help calm your fears if a condom ever breaks. (Trust me, that's really a scary couple weeks wait that is best avoided.)
You should also discuss the morning after pill. Now this could be a touchy subject-because some people do consider it abortion. But if there is ever a chance that the condom breaks in the future, and she is willing to take it, it could stop an unwanted pregnancy. Again, you have to talk to her about it because she may not be willing. But if she is, and one of you have it around just in case it really could make the difference. Remember it needs to be taken within 72 hours of unprotected sex and SHOULD NOT be taken more than a couple times a year because they're essentially a LARGE dose of hormones and can mess up a body if taken too much.
I think you're making first-time sex sound like it isn't much fun. :)
Since the condom stayed on, and the mishaps did not cause the penis to touch the vagina, and since you hadn't ejaculated when things slipped, I believe you did not get her pregnant.
The other factor to consider is how long it was after her last period. If she was not ovulating (which she only does one day in her menstrual month) even if you did have a mishap that caused semen to reach the vaginal fluids, it would not cause a pregnancy. Unfortunately, the date of ovulation is not easy to predict, but if she were very close to the day her next period was due, it is less likely.
Please don't have sex again this way, standing up, slipping condoms, pulling out before ejaculating and all, it sounds more unpleasant and mechanical than loving and caring.
She should get onto the pill and you should be using condoms, if you two intend to continue to be intimate.