Hi esmeralda – if you look around the forums you’ll see that this is a VERY common problem when it’s time for couples to transition to intercourse. Since so much time is usually spent on the woman’s development of being able to achieve penetration and their male partners often are not used to that possibility being on the table, the very prospect of it can overexcite men to the point of premature ejaculation.
The first thing to try may be just attempting sex more frequently or having your partner masturbate a few hours before you try to have intercourse (this will be an experiment for a little while to see what works). This is usually a temporary state of affairs and passes with time, so just keep at it and let us know what you’ve tried!