Question for you: Do you consider putting on a condom as a necessary evil to getting to have sex. If it is just something to do as quickly as possible so you can get to the good part, that may be your problem. Putting on the condom needs to be part of your foreplay. Have your girlfriend put it on you. Make it exciting. Tell her to use her imagination. I bet that if you slow down, make it an enjoyable part of the love making that you will be rock hard and give her a time she will never forget. Just slow down amd have a little fun. Oh, by the way, You really will need to make it up to her. Now, it is your turn to us your imagination.
Have a good time.