ok so after i ejaculate i just keep going and my girlfriend and i were wondering how is this possible?

According to some studies, 18-year-old males have a refractory period of about 15 minutes, while those in their 70s take about 20 hours, with the average for all men being about a half-hour. Although rarer, some males exhibit no refractory period or a refractory period lasting less than 10 seconds. A scientific study to successfully document natural, fully ejaculatory, multiple orgasms in an adult man was conducted at Rutgers University in 1995. During the study, six fully ejaculatory orgasms were experienced in 36 minutes, with no apparent refractory period.

I used to be able to stay hard and keep going. Enjoy it while it lasts because it won't.

Depends how old you are. If you're 18, you can go all night.